#!/usr/bin/env python3
"""
PR Overlap Detection Tool

Detects potential merge conflicts between a given PR and other open PRs
by checking for file overlap, line overlap, and actual merge conflicts.
"""

import json
import os
import re
import subprocess
import sys
import tempfile
from dataclasses import dataclass
from typing import Optional


# =============================================================================
# MAIN ENTRY POINT
# =============================================================================

def main():
    """Main entry point for PR overlap detection."""
    import argparse
    
    parser = argparse.ArgumentParser(description="Detect PR overlaps and potential merge conflicts")
    parser.add_argument("pr_number", type=int, help="PR number to check")
    parser.add_argument("--base", default=None, help="Base branch (default: auto-detect from PR)")
    parser.add_argument("--skip-merge-test", action="store_true", help="Skip actual merge conflict testing")
    parser.add_argument("--discord-webhook", default=os.environ.get("DISCORD_WEBHOOK_URL"), help="Discord webhook URL for notifications")
    parser.add_argument("--dry-run", action="store_true", help="Don't post comments, just print")
    
    args = parser.parse_args()
    
    owner, repo = get_repo_info()
    print(f"Checking PR #{args.pr_number} in {owner}/{repo}")
    
    # Get current PR info
    current_pr = fetch_pr_details(args.pr_number)
    base_branch = args.base or current_pr.base_ref
    
    print(f"PR #{current_pr.number}: {current_pr.title}")
    print(f"Base branch: {base_branch}")
    print(f"Files changed: {len(current_pr.files)}")
    
    # Find overlapping PRs
    overlaps, all_changes = find_overlapping_prs(
        owner, repo, base_branch, current_pr, args.pr_number, args.skip_merge_test
    )
    
    if not overlaps:
        print("No overlaps detected!")
        return
    
    # Generate and post report
    comment = format_comment(overlaps, args.pr_number, current_pr.changed_ranges, all_changes)
    
    if args.dry_run:
        print("\n" + "="*60)
        print("COMMENT PREVIEW:")
        print("="*60)
        print(comment)
    else:
        if comment:
            post_or_update_comment(args.pr_number, comment)
            print("Posted comment to PR")
        
        if args.discord_webhook:
            send_discord_notification(args.discord_webhook, current_pr, overlaps)
    
    # Report results and exit
    report_results(overlaps)


# =============================================================================
# HIGH-LEVEL WORKFLOW FUNCTIONS
# =============================================================================

def fetch_pr_details(pr_number: int) -> "PullRequest":
    """Fetch details for a specific PR including its diff."""
    result = run_gh(["pr", "view", str(pr_number), "--json", "number,title,url,author,headRefName,baseRefName,files"])
    data = json.loads(result.stdout)
    
    pr = PullRequest(
        number=data["number"],
        title=data["title"],
        author=data["author"]["login"] if data.get("author") else "unknown",
        url=data["url"],
        head_ref=data["headRefName"],
        base_ref=data["baseRefName"],
        files=[f["path"] for f in data["files"]],
        changed_ranges={}
    )
    
    # Get detailed diff
    diff = get_pr_diff(pr_number)
    pr.changed_ranges = parse_diff_ranges(diff)
    
    return pr


def find_overlapping_prs(
    owner: str,
    repo: str,
    base_branch: str,
    current_pr: "PullRequest",
    current_pr_number: int,
    skip_merge_test: bool
) -> tuple[list["Overlap"], dict[int, dict[str, "ChangedFile"]]]:
    """Find all PRs that overlap with the current PR."""
    # Query other open PRs
    all_prs = query_open_prs(owner, repo, base_branch)
    other_prs = [p for p in all_prs if p["number"] != current_pr_number]
    
    print(f"Found {len(other_prs)} other open PRs targeting {base_branch}")
    
    # Find file overlaps (excluding ignored files, filtering by age)
    candidates = find_file_overlap_candidates(current_pr.files, other_prs)
    
    print(f"Found {len(candidates)} PRs with file overlap (excluding ignored files)")
    
    if not candidates:
        return [], {}
    
    # First pass: analyze line overlaps (no merge testing yet)
    overlaps = []
    all_changes = {}
    prs_needing_merge_test = []
    
    for pr_data, shared_files in candidates:
        overlap, pr_changes = analyze_pr_overlap(
            owner, repo, base_branch, current_pr, pr_data, shared_files,
            skip_merge_test=True  # Always skip in first pass
        )
        if overlap:
            overlaps.append(overlap)
            all_changes[pr_data["number"]] = pr_changes
            # Track PRs that need merge testing
            if overlap.line_overlaps and not skip_merge_test:
                prs_needing_merge_test.append(overlap)
    
    # Second pass: batch merge testing with shared clone
    if prs_needing_merge_test:
        run_batch_merge_tests(owner, repo, base_branch, current_pr, prs_needing_merge_test)
    
    return overlaps, all_changes


def run_batch_merge_tests(
    owner: str,
    repo: str,
    base_branch: str,
    current_pr: "PullRequest",
    overlaps: list["Overlap"]
):
    """Run merge tests for multiple PRs using a shared clone."""
    with tempfile.TemporaryDirectory() as tmpdir:
        # Clone once
        if not clone_repo(owner, repo, base_branch, tmpdir):
            return
        
        configure_git(tmpdir)
        
        # Fetch current PR branch once
        result = run_git(["fetch", "origin", f"pull/{current_pr.number}/head:pr-{current_pr.number}"], cwd=tmpdir, check=False)
        if result.returncode != 0:
            print(f"Warning: Could not fetch current PR #{current_pr.number}", file=sys.stderr)
            return
        
        for overlap in overlaps:
            other_pr = overlap.pr_b if overlap.pr_a.number == current_pr.number else overlap.pr_a
            print(f"Testing merge conflict with PR #{other_pr.number}...", flush=True)
            
            # Clean up any in-progress merge from previous iteration
            run_git(["merge", "--abort"], cwd=tmpdir, check=False)
            
            # Reset to base branch
            run_git(["checkout", base_branch], cwd=tmpdir, check=False)
            run_git(["reset", "--hard", f"origin/{base_branch}"], cwd=tmpdir, check=False)
            run_git(["clean", "-fdx"], cwd=tmpdir, check=False)
            
            # Fetch the other PR branch
            result = run_git(["fetch", "origin", f"pull/{other_pr.number}/head:pr-{other_pr.number}"], cwd=tmpdir, check=False)
            if result.returncode != 0:
                print(f"Warning: Could not fetch PR #{other_pr.number}: {result.stderr.strip()}", file=sys.stderr)
                continue
            
            # Try merging current PR first
            result = run_git(["merge", "--no-commit", "--no-ff", f"pr-{current_pr.number}"], cwd=tmpdir, check=False)
            if result.returncode != 0:
                # Current PR conflicts with base
                conflict_files, conflict_details = extract_conflict_info(tmpdir, result.stderr)
                overlap.has_merge_conflict = True
                overlap.conflict_files = conflict_files
                overlap.conflict_details = conflict_details
                overlap.conflict_type = 'pr_a_conflicts_base'
                run_git(["merge", "--abort"], cwd=tmpdir, check=False)
                continue
            
            # Commit and try merging other PR
            run_git(["commit", "-m", f"Merge PR #{current_pr.number}"], cwd=tmpdir, check=False)
            
            result = run_git(["merge", "--no-commit", "--no-ff", f"pr-{other_pr.number}"], cwd=tmpdir, check=False)
            if result.returncode != 0:
                # Conflict between PRs
                conflict_files, conflict_details = extract_conflict_info(tmpdir, result.stderr)
                overlap.has_merge_conflict = True
                overlap.conflict_files = conflict_files
                overlap.conflict_details = conflict_details
                overlap.conflict_type = 'conflict'
                run_git(["merge", "--abort"], cwd=tmpdir, check=False)


def analyze_pr_overlap(
    owner: str,
    repo: str,
    base_branch: str,
    current_pr: "PullRequest",
    other_pr_data: dict,
    shared_files: list[str],
    skip_merge_test: bool
) -> tuple[Optional["Overlap"], dict[str, "ChangedFile"]]:
    """Analyze overlap between current PR and another PR."""
    # Filter out ignored files
    non_ignored_shared = [f for f in shared_files if not should_ignore_file(f)]
    if not non_ignored_shared:
        return None, {}
    
    other_pr = PullRequest(
        number=other_pr_data["number"],
        title=other_pr_data["title"],
        author=other_pr_data["author"],
        url=other_pr_data["url"],
        head_ref=other_pr_data["head_ref"],
        base_ref=other_pr_data["base_ref"],
        files=other_pr_data["files"],
        changed_ranges={},
        updated_at=other_pr_data.get("updated_at")
    )
    
    # Get diff for other PR
    other_diff = get_pr_diff(other_pr.number)
    other_pr.changed_ranges = parse_diff_ranges(other_diff)
    
    # Check line overlaps
    line_overlaps = find_line_overlaps(
        current_pr.changed_ranges,
        other_pr.changed_ranges,
        shared_files
    )
    
    overlap = Overlap(
        pr_a=current_pr,
        pr_b=other_pr,
        overlapping_files=non_ignored_shared,
        line_overlaps=line_overlaps
    )
    
    # Test for actual merge conflicts if we have line overlaps
    if line_overlaps and not skip_merge_test:
        print(f"Testing merge conflict with PR #{other_pr.number}...", flush=True)
        has_conflict, conflict_files, conflict_details, error_type = test_merge_conflict(
            owner, repo, base_branch, current_pr, other_pr
        )
        overlap.has_merge_conflict = has_conflict
        overlap.conflict_files = conflict_files
        overlap.conflict_details = conflict_details
        overlap.conflict_type = error_type
    
    return overlap, other_pr.changed_ranges


def find_file_overlap_candidates(
    current_files: list[str],
    other_prs: list[dict],
    max_age_days: int = 14
) -> list[tuple[dict, list[str]]]:
    """Find PRs that share files with the current PR."""
    from datetime import datetime, timezone, timedelta
    
    current_files_set = set(f for f in current_files if not should_ignore_file(f))
    candidates = []
    cutoff_date = datetime.now(timezone.utc) - timedelta(days=max_age_days)
    
    for pr_data in other_prs:
        # Filter out PRs older than max_age_days
        updated_at = pr_data.get("updated_at")
        if updated_at:
            try:
                pr_date = datetime.fromisoformat(updated_at.replace('Z', '+00:00'))
                if pr_date < cutoff_date:
                    continue  # Skip old PRs
            except Exception as e:
                # If we can't parse date, include the PR (safe fallback)
                print(f"Warning: Could not parse date for PR: {e}", file=sys.stderr)
        
        other_files = set(f for f in pr_data["files"] if not should_ignore_file(f))
        shared = current_files_set & other_files
        
        if shared:
            candidates.append((pr_data, list(shared)))
    
    return candidates


def report_results(overlaps: list["Overlap"]):
    """Report results (informational only, always exits 0)."""
    conflicts = [o for o in overlaps if o.has_merge_conflict]
    if conflicts:
        print(f"\n⚠️  Found {len(conflicts)} merge conflict(s)")
    
    line_overlap_count = len([o for o in overlaps if o.line_overlaps])
    if line_overlap_count:
        print(f"\n⚠️  Found {line_overlap_count} PR(s) with line overlap")
    
    print("\n✅ Done")
    # Always exit 0 - this check is informational, not a merge blocker


# =============================================================================
# COMMENT FORMATTING
# =============================================================================

def format_comment(
    overlaps: list["Overlap"],
    current_pr: int,
    changes_current: dict[str, "ChangedFile"],
    all_changes: dict[int, dict[str, "ChangedFile"]]
) -> str:
    """Format the overlap report as a PR comment."""
    if not overlaps:
        return ""
    
    lines = ["## 🔍 PR Overlap Detection"]
    lines.append("")
    lines.append("This check compares your PR against all other open PRs targeting the same branch to detect potential merge conflicts early.")
    lines.append("")
    
    # Check if current PR conflicts with base branch
    format_base_conflicts(overlaps, lines)
    
    # Classify and sort overlaps
    classified = classify_all_overlaps(overlaps, current_pr, changes_current, all_changes)
    
    # Group by risk
    conflicts = [(o, r) for o, r in classified if r == 'conflict']
    medium_risk = [(o, r) for o, r in classified if r == 'medium']
    low_risk = [(o, r) for o, r in classified if r == 'low']
    
    # Format each section
    format_conflicts_section(conflicts, current_pr, lines)
    format_medium_risk_section(medium_risk, current_pr, changes_current, all_changes, lines)
    format_low_risk_section(low_risk, current_pr, lines)
    
    # Summary
    total = len(overlaps)
    lines.append(f"\n**Summary:** {len(conflicts)} conflict(s), {len(medium_risk)} medium risk, {len(low_risk)} low risk (out of {total} PRs with file overlap)")
    lines.append("\n---\n*Auto-generated on push. Ignores: `openapi.json`, lock files.*")
    
    return "\n".join(lines)


def format_base_conflicts(overlaps: list["Overlap"], lines: list[str]):
    """Format base branch conflicts section."""
    base_conflicts = [o for o in overlaps if o.conflict_type == 'pr_a_conflicts_base']
    if base_conflicts:
        lines.append("### ⚠️ This PR has conflicts with the base branch\n")
        lines.append("Conflicts will need to be resolved before merging:\n")
        first = base_conflicts[0]
        for f in first.conflict_files[:10]:
            lines.append(f"- `{f}`")
        if len(first.conflict_files) > 10:
            lines.append(f"- ... and {len(first.conflict_files) - 10} more files")
        lines.append("\n")


def format_conflicts_section(conflicts: list[tuple], current_pr: int, lines: list[str]):
    """Format the merge conflicts section."""
    pr_conflicts = [(o, r) for o, r in conflicts if o.conflict_type != 'pr_a_conflicts_base']
    
    if not pr_conflicts:
        return
    
    lines.append("### 🔴 Merge Conflicts Detected")
    lines.append("")
    lines.append("The following PRs have been tested and **will have merge conflicts** if merged after this PR. Consider coordinating with the authors.")
    lines.append("")
    
    for o, _ in pr_conflicts:
        other = o.pr_b if o.pr_a.number == current_pr else o.pr_a
        format_pr_entry(other, lines)
        format_conflict_details(o, lines)
        lines.append("")


def format_medium_risk_section(
    medium_risk: list[tuple],
    current_pr: int,
    changes_current: dict,
    all_changes: dict,
    lines: list[str]
):
    """Format the medium risk section."""
    if not medium_risk:
        return
    
    lines.append("### 🟡 Medium Risk — Some Line Overlap\n")
    lines.append("These PRs have some overlapping changes:\n")
    
    for o, _ in medium_risk:
        other = o.pr_b if o.pr_a.number == current_pr else o.pr_a
        other_changes = all_changes.get(other.number, {})
        format_pr_entry(other, lines)
        
        # Note if rename is involved
        for file_path in o.overlapping_files:
            file_a = changes_current.get(file_path)
            file_b = other_changes.get(file_path)
            if (file_a and file_a.is_rename) or (file_b and file_b.is_rename):
                lines.append(f"  - ⚠️ `{file_path}` is being renamed/moved")
                break
        
        if o.line_overlaps:
            for file_path, ranges in o.line_overlaps.items():
                range_strs = [f"L{r[0]}-{r[1]}" if r[0] != r[1] else f"L{r[0]}" for r in ranges]
                lines.append(f"  - `{file_path}`: {', '.join(range_strs)}")
        else:
            non_ignored = [f for f in o.overlapping_files if not should_ignore_file(f)]
            if non_ignored:
                lines.append(f"  - Shared files: `{'`, `'.join(non_ignored[:5])}`")
        lines.append("")


def format_low_risk_section(low_risk: list[tuple], current_pr: int, lines: list[str]):
    """Format the low risk section."""
    if not low_risk:
        return
    
    lines.append("### 🟢 Low Risk — File Overlap Only\n")
    lines.append("<details><summary>These PRs touch the same files but different sections (click to expand)</summary>\n")
    
    for o, _ in low_risk:
        other = o.pr_b if o.pr_a.number == current_pr else o.pr_a
        non_ignored = [f for f in o.overlapping_files if not should_ignore_file(f)]
        if non_ignored:
            format_pr_entry(other, lines)
            if o.line_overlaps:
                for file_path, ranges in o.line_overlaps.items():
                    range_strs = [f"L{r[0]}-{r[1]}" if r[0] != r[1] else f"L{r[0]}" for r in ranges]
                    lines.append(f"  - `{file_path}`: {', '.join(range_strs)}")
            else:
                lines.append(f"  - Shared files: `{'`, `'.join(non_ignored[:5])}`")
            lines.append("")  # Add blank line between entries
    
    lines.append("</details>\n")


def format_pr_entry(pr: "PullRequest", lines: list[str]):
    """Format a single PR entry line."""
    updated = format_relative_time(pr.updated_at)
    updated_str = f" · updated {updated}" if updated else ""
    # Just use #number - GitHub auto-renders it with title
    lines.append(f"- #{pr.number} ({pr.author}{updated_str})")


def format_conflict_details(overlap: "Overlap", lines: list[str]):
    """Format conflict details for a PR."""
    if overlap.conflict_details:
        all_paths = [d.path for d in overlap.conflict_details]
        common_prefix = find_common_prefix(all_paths)
        if common_prefix:
            lines.append(f"  - 📁 `{common_prefix}`")
        for detail in overlap.conflict_details:
            display_path = detail.path[len(common_prefix):] if common_prefix else detail.path
            size_str = format_conflict_size(detail)
            lines.append(f"    - `{display_path}`{size_str}")
    elif overlap.conflict_files:
        common_prefix = find_common_prefix(overlap.conflict_files)
        if common_prefix:
            lines.append(f"  - 📁 `{common_prefix}`")
        for f in overlap.conflict_files:
            display_path = f[len(common_prefix):] if common_prefix else f
            lines.append(f"    - `{display_path}`")


def format_conflict_size(detail: "ConflictInfo") -> str:
    """Format conflict size string for a file."""
    if detail.conflict_count > 0:
        return f" ({detail.conflict_count} conflict{'s' if detail.conflict_count > 1 else ''}, ~{detail.conflict_lines} lines)"
    elif detail.conflict_type != 'content':
        type_labels = {
            'both_added': 'added in both',
            'both_deleted': 'deleted in both',
            'deleted_by_us': 'deleted here, modified there',
            'deleted_by_them': 'modified here, deleted there',
            'added_by_us': 'added here',
            'added_by_them': 'added there',
        }
        label = type_labels.get(detail.conflict_type, detail.conflict_type)
        return f" ({label})"
    return ""


def format_line_overlaps(line_overlaps: dict[str, list[tuple]], lines: list[str]):
    """Format line overlap details."""
    all_paths = list(line_overlaps.keys())
    common_prefix = find_common_prefix(all_paths) if len(all_paths) > 1 else ""
    if common_prefix:
        lines.append(f"  - 📁 `{common_prefix}`")
    for file_path, ranges in line_overlaps.items():
        display_path = file_path[len(common_prefix):] if common_prefix else file_path
        range_strs = [f"L{r[0]}-{r[1]}" if r[0] != r[1] else f"L{r[0]}" for r in ranges]
        indent = "    " if common_prefix else "  "
        lines.append(f"{indent}- `{display_path}`: {', '.join(range_strs)}")


# =============================================================================
# OVERLAP ANALYSIS
# =============================================================================

def classify_all_overlaps(
    overlaps: list["Overlap"],
    current_pr: int,
    changes_current: dict,
    all_changes: dict
) -> list[tuple["Overlap", str]]:
    """Classify all overlaps by risk level and sort them."""
    classified = []
    for o in overlaps:
        other_pr = o.pr_b if o.pr_a.number == current_pr else o.pr_a
        other_changes = all_changes.get(other_pr.number, {})
        risk = classify_overlap_risk(o, changes_current, other_changes)
        classified.append((o, risk))
    
    def sort_key(item):
        o, risk = item
        risk_order = {'conflict': 0, 'medium': 1, 'low': 2}
        # For conflicts, also sort by total conflict lines (descending)
        conflict_lines = sum(d.conflict_lines for d in o.conflict_details) if o.conflict_details else 0
        return (risk_order.get(risk, 99), -conflict_lines)
    
    classified.sort(key=sort_key)
    
    return classified


def classify_overlap_risk(
    overlap: "Overlap",
    changes_a: dict[str, "ChangedFile"],
    changes_b: dict[str, "ChangedFile"]
) -> str:
    """Classify the risk level of an overlap."""
    if overlap.has_merge_conflict:
        return 'conflict'
    
    has_rename = any(
        (changes_a.get(f) and changes_a[f].is_rename) or 
        (changes_b.get(f) and changes_b[f].is_rename)
        for f in overlap.overlapping_files
    )
    
    if overlap.line_overlaps:
        total_overlap_lines = sum(
            end - start + 1
            for ranges in overlap.line_overlaps.values()
            for start, end in ranges
        )
        
        # Medium risk: >20 lines overlap or file rename
        if total_overlap_lines > 20 or has_rename:
            return 'medium'
        else:
            return 'low'
    
    if has_rename:
        return 'medium'
    
    return 'low'


def find_line_overlaps(
    changes_a: dict[str, "ChangedFile"],
    changes_b: dict[str, "ChangedFile"],
    shared_files: list[str]
) -> dict[str, list[tuple[int, int]]]:
    """Find overlapping line ranges in shared files."""
    overlaps = {}
    
    for file_path in shared_files:
        if should_ignore_file(file_path):
            continue
        
        file_a = changes_a.get(file_path)
        file_b = changes_b.get(file_path)
        
        if not file_a or not file_b:
            continue
        
        # Skip pure renames
        if file_a.is_rename and not file_a.additions and not file_a.deletions:
            continue
        if file_b.is_rename and not file_b.additions and not file_b.deletions:
            continue
        
        # Note: This mixes old-file (deletions) and new-file (additions) line numbers,
        # which can cause false positives when PRs insert/remove many lines.
        # Acceptable for v1 since the real merge test is the authoritative check.
        file_overlaps = find_range_overlaps(
            file_a.additions + file_a.deletions,
            file_b.additions + file_b.deletions
        )
        
        if file_overlaps:
            overlaps[file_path] = merge_ranges(file_overlaps)
    
    return overlaps


def find_range_overlaps(
    ranges_a: list[tuple[int, int]],
    ranges_b: list[tuple[int, int]]
) -> list[tuple[int, int]]:
    """Find overlapping regions between two sets of ranges."""
    overlaps = []
    for range_a in ranges_a:
        for range_b in ranges_b:
            if ranges_overlap(range_a, range_b):
                overlap_start = max(range_a[0], range_b[0])
                overlap_end = min(range_a[1], range_b[1])
                overlaps.append((overlap_start, overlap_end))
    return overlaps


def ranges_overlap(range_a: tuple[int, int], range_b: tuple[int, int]) -> bool:
    """Check if two line ranges overlap."""
    return range_a[0] <= range_b[1] and range_b[0] <= range_a[1]


def merge_ranges(ranges: list[tuple[int, int]]) -> list[tuple[int, int]]:
    """Merge overlapping line ranges."""
    if not ranges:
        return []
    
    sorted_ranges = sorted(ranges, key=lambda x: x[0])
    merged = [sorted_ranges[0]]
    
    for current in sorted_ranges[1:]:
        last = merged[-1]
        if current[0] <= last[1] + 1:
            merged[-1] = (last[0], max(last[1], current[1]))
        else:
            merged.append(current)
    
    return merged


# =============================================================================
# MERGE CONFLICT TESTING
# =============================================================================

def test_merge_conflict(
    owner: str,
    repo: str,
    base_branch: str,
    pr_a: "PullRequest",
    pr_b: "PullRequest"
) -> tuple[bool, list[str], list["ConflictInfo"], str]:
    """Test if merging both PRs would cause a conflict."""
    with tempfile.TemporaryDirectory() as tmpdir:
        # Clone repo
        if not clone_repo(owner, repo, base_branch, tmpdir):
            return False, [], [], None
        
        configure_git(tmpdir)
        if not fetch_pr_branches(tmpdir, pr_a.number, pr_b.number):
            # Fetch failed for one or both PRs - can't test merge
            return False, [], [], None
        
        # Try merging PR A first
        conflict_result = try_merge_pr(tmpdir, pr_a.number)
        if conflict_result:
            return True, conflict_result[0], conflict_result[1], 'pr_a_conflicts_base'
        
        # Commit and try merging PR B
        run_git(["commit", "-m", f"Merge PR #{pr_a.number}"], cwd=tmpdir, check=False)
        
        conflict_result = try_merge_pr(tmpdir, pr_b.number)
        if conflict_result:
            return True, conflict_result[0], conflict_result[1], 'conflict'
        
        return False, [], [], None


def clone_repo(owner: str, repo: str, branch: str, tmpdir: str) -> bool:
    """Clone the repository."""
    clone_url = f"https://github.com/{owner}/{repo}.git"
    result = run_git(
        ["clone", "--depth=50", "--branch", branch, clone_url, tmpdir],
        check=False
    )
    if result.returncode != 0:
        print(f"Failed to clone: {result.stderr}", file=sys.stderr)
        return False
    return True


def configure_git(tmpdir: str):
    """Configure git for commits."""
    run_git(["config", "user.email", "github-actions[bot]@users.noreply.github.com"], cwd=tmpdir, check=False)
    run_git(["config", "user.name", "github-actions[bot]"], cwd=tmpdir, check=False)


def fetch_pr_branches(tmpdir: str, pr_a: int, pr_b: int) -> bool:
    """Fetch both PR branches. Returns False if any fetch fails."""
    success = True
    for pr_num in (pr_a, pr_b):
        result = run_git(["fetch", "origin", f"pull/{pr_num}/head:pr-{pr_num}"], cwd=tmpdir, check=False)
        if result.returncode != 0:
            print(f"Warning: Could not fetch PR #{pr_num}: {result.stderr.strip()}", file=sys.stderr)
            success = False
    return success


def try_merge_pr(tmpdir: str, pr_number: int) -> Optional[tuple[list[str], list["ConflictInfo"]]]:
    """Try to merge a PR. Returns conflict info if conflicts, None if success."""
    result = run_git(["merge", "--no-commit", "--no-ff", f"pr-{pr_number}"], cwd=tmpdir, check=False)
    
    if result.returncode == 0:
        return None
    
    # Conflict detected
    conflict_files, conflict_details = extract_conflict_info(tmpdir, result.stderr)
    run_git(["merge", "--abort"], cwd=tmpdir, check=False)
    
    return conflict_files, conflict_details


def extract_conflict_info(tmpdir: str, stderr: str) -> tuple[list[str], list["ConflictInfo"]]:
    """Extract conflict information from git status."""
    status_result = run_git(["status", "--porcelain"], cwd=tmpdir, check=False)
    
    status_types = {
        'UU': 'content',
        'AA': 'both_added',
        'DD': 'both_deleted',
        'DU': 'deleted_by_us',
        'UD': 'deleted_by_them',
        'AU': 'added_by_us',
        'UA': 'added_by_them',
    }
    
    conflict_files = []
    conflict_details = []
    
    for line in status_result.stdout.split("\n"):
        if len(line) >= 3 and line[0:2] in status_types:
            status_code = line[0:2]
            file_path = line[3:].strip()
            conflict_files.append(file_path)
            
            info = analyze_conflict_markers(file_path, tmpdir)
            info.conflict_type = status_types.get(status_code, 'unknown')
            conflict_details.append(info)
    
    # Fallback to stderr parsing
    if not conflict_files and stderr:
        for line in stderr.split("\n"):
            if "CONFLICT" in line and ":" in line:
                parts = line.split(":")
                if len(parts) > 1:
                    file_part = parts[-1].strip()
                    if file_part and not file_part.startswith("Merge"):
                        conflict_files.append(file_part)
                        conflict_details.append(ConflictInfo(path=file_part))
    
    return conflict_files, conflict_details


def analyze_conflict_markers(file_path: str, cwd: str) -> "ConflictInfo":
    """Analyze a conflicted file to count conflict regions and lines."""
    info = ConflictInfo(path=file_path)
    
    try:
        full_path = os.path.join(cwd, file_path)
        with open(full_path, 'r', errors='ignore') as f:
            content = f.read()
        
        in_conflict = False
        current_conflict_lines = 0
        
        for line in content.split('\n'):
            if line.startswith('<<<<<<<'):
                in_conflict = True
                info.conflict_count += 1
                current_conflict_lines = 1
            elif line.startswith('>>>>>>>'):
                in_conflict = False
                current_conflict_lines += 1
                info.conflict_lines += current_conflict_lines
            elif in_conflict:
                current_conflict_lines += 1
    except Exception as e:
        print(f"Warning: Could not analyze conflict markers in {file_path}: {e}", file=sys.stderr)
    
    return info


# =============================================================================
# DIFF PARSING
# =============================================================================

def parse_diff_ranges(diff: str) -> dict[str, "ChangedFile"]:
    """Parse a unified diff and extract changed line ranges per file."""
    files = {}
    current_file = None
    pending_rename_from = None
    is_rename = False
    
    for line in diff.split("\n"):
        # Reset rename state on new file diff header
        if line.startswith("diff --git "):
            is_rename = False
            pending_rename_from = None
        elif line.startswith("rename from "):
            pending_rename_from = line[12:]
            is_rename = True
        elif line.startswith("rename to "):
            pass  # rename target is captured via "+++ b/" line
        elif line.startswith("similarity index"):
            is_rename = True
        elif line.startswith("+++ b/"):
            path = line[6:]
            current_file = ChangedFile(
                path=path,
                additions=[],
                deletions=[],
                is_rename=is_rename,
                old_path=pending_rename_from
            )
            files[path] = current_file
            pending_rename_from = None
            is_rename = False
        elif line.startswith("--- /dev/null"):
            is_rename = False
            pending_rename_from = None
        elif line.startswith("@@") and current_file:
            parse_hunk_header(line, current_file)
    
    return files


def parse_hunk_header(line: str, current_file: "ChangedFile"):
    """Parse a diff hunk header and add ranges to the file."""
    match = re.match(r"@@ -(\d+)(?:,(\d+))? \+(\d+)(?:,(\d+))? @@", line)
    if match:
        old_start = int(match.group(1))
        old_count = int(match.group(2) or 1)
        new_start = int(match.group(3))
        new_count = int(match.group(4) or 1)
        
        if old_count > 0:
            current_file.deletions.append((old_start, old_start + old_count - 1))
        if new_count > 0:
            current_file.additions.append((new_start, new_start + new_count - 1))


# =============================================================================
# GITHUB API
# =============================================================================

def get_repo_info() -> tuple[str, str]:
    """Get owner and repo name from environment or git."""
    if os.environ.get("GITHUB_REPOSITORY"):
        owner, repo = os.environ["GITHUB_REPOSITORY"].split("/")
        return owner, repo
    
    result = run_gh(["repo", "view", "--json", "owner,name"])
    data = json.loads(result.stdout)
    return data["owner"]["login"], data["name"]


def query_open_prs(owner: str, repo: str, base_branch: str) -> list[dict]:
    """Query all open PRs targeting the specified base branch."""
    prs = []
    cursor = None
    
    while True:
        after_clause = f', after: "{cursor}"' if cursor else ""
        query = f'''
        query {{
            repository(owner: "{owner}", name: "{repo}") {{
                pullRequests(
                    first: 100{after_clause},
                    states: OPEN,
                    baseRefName: "{base_branch}",
                    orderBy: {{field: UPDATED_AT, direction: DESC}}
                ) {{
                    totalCount
                    edges {{
                        node {{
                            number
                            title
                            url
                            updatedAt
                            author {{ login }}
                            headRefName
                            baseRefName
                            files(first: 100) {{
                                nodes {{ path }}
                                pageInfo {{ hasNextPage }}
                            }}
                        }}
                    }}
                    pageInfo {{
                        endCursor
                        hasNextPage
                    }}
                }}
            }}
        }}
        '''
        
        result = run_gh(["api", "graphql", "-f", f"query={query}"])
        data = json.loads(result.stdout)
        
        if "errors" in data:
            print(f"GraphQL errors: {data['errors']}", file=sys.stderr)
            sys.exit(1)
        
        pr_data = data["data"]["repository"]["pullRequests"]
        for edge in pr_data["edges"]:
            node = edge["node"]
            files_data = node["files"]
            # Warn if PR has more than 100 files (API limit, we only fetch first 100)
            if files_data.get("pageInfo", {}).get("hasNextPage"):
                print(f"Warning: PR #{node['number']} has >100 files, overlap detection may be incomplete", file=sys.stderr)
            prs.append({
                "number": node["number"],
                "title": node["title"],
                "url": node["url"],
                "updated_at": node.get("updatedAt"),
                "author": node["author"]["login"] if node["author"] else "unknown",
                "head_ref": node["headRefName"],
                "base_ref": node["baseRefName"],
                "files": [f["path"] for f in files_data["nodes"]]
            })
        
        if not pr_data["pageInfo"]["hasNextPage"]:
            break
        cursor = pr_data["pageInfo"]["endCursor"]
    
    return prs


def get_pr_diff(pr_number: int) -> str:
    """Get the diff for a PR."""
    result = run_gh(["pr", "diff", str(pr_number)])
    return result.stdout


def post_or_update_comment(pr_number: int, body: str):
    """Post a new comment or update existing overlap detection comment."""
    if not body:
        return
    
    marker = "## 🔍 PR Overlap Detection"
    
    # Find existing comment using GraphQL
    owner, repo = get_repo_info()
    query = f'''
    query {{
        repository(owner: "{owner}", name: "{repo}") {{
            pullRequest(number: {pr_number}) {{
                comments(first: 100) {{
                    nodes {{
                        id
                        body
                        author {{ login }}
                    }}
                }}
            }}
        }}
    }}
    '''
    
    result = run_gh(["api", "graphql", "-f", f"query={query}"], check=False)
    
    existing_comment_id = None
    if result.returncode == 0:
        try:
            data = json.loads(result.stdout)
            comments = data.get("data", {}).get("repository", {}).get("pullRequest", {}).get("comments", {}).get("nodes", [])
            for comment in comments:
                if marker in comment.get("body", ""):
                    existing_comment_id = comment["id"]
                    break
        except Exception as e:
            print(f"Warning: Could not search for existing comment: {e}", file=sys.stderr)
    
    if existing_comment_id:
        # Update existing comment using GraphQL mutation
        # Use json.dumps for proper escaping of all special characters
        escaped_body = json.dumps(body)[1:-1]  # Strip outer quotes added by json.dumps
        mutation = f'''
        mutation {{
            updateIssueComment(input: {{id: "{existing_comment_id}", body: "{escaped_body}"}}) {{
                issueComment {{ id }}
            }}
        }}
        '''
        result = run_gh(["api", "graphql", "-f", f"query={mutation}"], check=False)
        if result.returncode == 0:
            print(f"Updated existing overlap comment")
        else:
            # Fallback to posting new comment
            print(f"Failed to update comment, posting new one: {result.stderr}", file=sys.stderr)
            run_gh(["pr", "comment", str(pr_number), "--body", body])
    else:
        # Post new comment
        run_gh(["pr", "comment", str(pr_number), "--body", body])


def send_discord_notification(webhook_url: str, pr: "PullRequest", overlaps: list["Overlap"]):
    """Send a Discord notification about significant overlaps."""
    conflicts = [o for o in overlaps if o.has_merge_conflict]
    if not conflicts:
        return
    
    # Discord limits: max 25 fields, max 1024 chars per field value
    fields = []
    for o in conflicts[:25]:
        other = o.pr_b if o.pr_a.number == pr.number else o.pr_a
        # Build value string with truncation to stay under 1024 chars
        file_list = o.conflict_files[:3]
        files_str = f"Files: `{'`, `'.join(file_list)}`"
        if len(o.conflict_files) > 3:
            files_str += f" (+{len(o.conflict_files) - 3} more)"
        value = f"[{other.title[:100]}]({other.url})\n{files_str}"
        # Truncate if still too long
        if len(value) > 1024:
            value = value[:1020] + "..."
        fields.append({
            "name": f"Conflicts with #{other.number}",
            "value": value,
            "inline": False
        })
    
    embed = {
        "title": f"⚠️ PR #{pr.number} has merge conflicts",
        "description": f"[{pr.title}]({pr.url})",
        "color": 0xFF0000,
        "fields": fields
    }
    
    if len(conflicts) > 25:
        embed["footer"] = {"text": f"... and {len(conflicts) - 25} more conflicts"}
    
    try:
        subprocess.run(
            ["curl", "-X", "POST", "-H", "Content-Type: application/json",
             "--max-time", "10",
             "-d", json.dumps({"embeds": [embed]}), webhook_url],
            capture_output=True,
            timeout=15
        )
    except subprocess.TimeoutExpired:
        print("Warning: Discord webhook timed out", file=sys.stderr)


# =============================================================================
# UTILITIES
# =============================================================================

def run_gh(args: list[str], check: bool = True) -> subprocess.CompletedProcess:
    """Run a gh CLI command."""
    result = subprocess.run(
        ["gh"] + args,
        capture_output=True,
        text=True,
        check=False
    )
    if check and result.returncode != 0:
        print(f"Error running gh {' '.join(args)}: {result.stderr}", file=sys.stderr)
        sys.exit(1)
    return result


def run_git(args: list[str], cwd: str = None, check: bool = True) -> subprocess.CompletedProcess:
    """Run a git command."""
    result = subprocess.run(
        ["git"] + args,
        capture_output=True,
        text=True,
        cwd=cwd,
        check=False
    )
    if check and result.returncode != 0:
        print(f"Error running git {' '.join(args)}: {result.stderr}", file=sys.stderr)
    return result


def should_ignore_file(path: str) -> bool:
    """Check if a file should be ignored for overlap detection."""
    if path in IGNORE_FILES:
        return True
    basename = path.split("/")[-1]
    return basename in IGNORE_FILES


def find_common_prefix(paths: list[str]) -> str:
    """Find the common directory prefix of a list of file paths."""
    if not paths:
        return ""
    if len(paths) == 1:
        parts = paths[0].rsplit('/', 1)
        return parts[0] + '/' if len(parts) > 1 else ""
    
    split_paths = [p.split('/') for p in paths]
    common = []
    for parts in zip(*split_paths):
        if len(set(parts)) == 1:
            common.append(parts[0])
        else:
            break
    
    return '/'.join(common) + '/' if common else ""


def format_relative_time(iso_timestamp: str) -> str:
    """Format an ISO timestamp as relative time."""
    if not iso_timestamp:
        return ""
    
    from datetime import datetime, timezone
    try:
        dt = datetime.fromisoformat(iso_timestamp.replace('Z', '+00:00'))
        now = datetime.now(timezone.utc)
        diff = now - dt
        
        seconds = diff.total_seconds()
        if seconds < 60:
            return "just now"
        elif seconds < 3600:
            return f"{int(seconds / 60)}m ago"
        elif seconds < 86400:
            return f"{int(seconds / 3600)}h ago"
        else:
            return f"{int(seconds / 86400)}d ago"
    except Exception as e:
        print(f"Warning: Could not format relative time: {e}", file=sys.stderr)
        return ""


# =============================================================================
# DATA CLASSES
# =============================================================================

@dataclass
class ChangedFile:
    """Represents a file changed in a PR."""
    path: str
    additions: list[tuple[int, int]]
    deletions: list[tuple[int, int]]
    is_rename: bool = False
    old_path: str = None


@dataclass
class PullRequest:
    """Represents a pull request."""
    number: int
    title: str
    author: str
    url: str
    head_ref: str
    base_ref: str
    files: list[str]
    changed_ranges: dict[str, ChangedFile]
    updated_at: str = None


@dataclass
class ConflictInfo:
    """Info about a single conflicting file."""
    path: str
    conflict_count: int = 0
    conflict_lines: int = 0
    conflict_type: str = "content"


@dataclass
class Overlap:
    """Represents an overlap between two PRs."""
    pr_a: PullRequest
    pr_b: PullRequest
    overlapping_files: list[str]
    line_overlaps: dict[str, list[tuple[int, int]]]
    has_merge_conflict: bool = False
    conflict_files: list[str] = None
    conflict_details: list[ConflictInfo] = None
    conflict_type: str = None

    def __post_init__(self):
        if self.conflict_files is None:
            self.conflict_files = []
        if self.conflict_details is None:
            self.conflict_details = []


# =============================================================================
# CONSTANTS
# =============================================================================

IGNORE_FILES = {
    "autogpt_platform/frontend/src/app/api/openapi.json",
    "poetry.lock",
    "pnpm-lock.yaml",
    "package-lock.json",
    "yarn.lock",
}


# =============================================================================
# ENTRY POINT
# =============================================================================

if __name__ == "__main__":
    main()