// Copyright 2025 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package postgreslistschemas

import (
	"context"
	"fmt"

	yaml "github.com/goccy/go-yaml"
	"github.com/googleapis/genai-toolbox/internal/sources"
	"github.com/googleapis/genai-toolbox/internal/tools"
	"github.com/googleapis/genai-toolbox/internal/util/parameters"
	"github.com/jackc/pgx/v5/pgxpool"
)

const kind string = "postgres-list-schemas"

const listSchemasStatement = `
	WITH
    schema_grants AS (
        SELECT schema_oid, jsonb_object_agg(grantee, privileges) AS grants
        FROM
        (
            SELECT
            n.oid AS schema_oid,
            CASE
                WHEN p.grantee = 0 THEN 'PUBLIC'
                ELSE pg_catalog.pg_get_userbyid(p.grantee)
                END
                AS grantee,
            jsonb_agg(p.privilege_type ORDER BY p.privilege_type) AS privileges
            FROM pg_catalog.pg_namespace n, aclexplode(n.nspacl) p
            WHERE n.nspacl IS NOT NULL
            GROUP BY n.oid, grantee
        ) permissions_by_grantee
        GROUP BY schema_oid
    ),
    all_schemas AS (
        SELECT
        n.nspname AS schema_name,
        pg_catalog.pg_get_userbyid(n.nspowner) AS owner,
		COALESCE(sg.grants, '{}'::jsonb) AS grants,
		(
			SELECT COUNT(*)
			FROM pg_catalog.pg_class c
			WHERE c.relnamespace = n.oid AND c.relkind = 'r'
		) AS tables,
		(
			SELECT COUNT(*)
			FROM pg_catalog.pg_class c
			WHERE c.relnamespace = n.oid AND c.relkind = 'v'
		) AS views,
		(SELECT COUNT(*) FROM pg_catalog.pg_proc p WHERE p.pronamespace = n.oid)
			AS functions
        FROM pg_catalog.pg_namespace n
        LEFT JOIN schema_grants sg
        ON n.oid = sg.schema_oid
    )
	SELECT *
	FROM all_schemas
    -- Exclude system schemas and temporary schemas created per session.
	WHERE
        schema_name NOT IN ('pg_catalog', 'information_schema', 'pg_toast')
        AND schema_name NOT LIKE 'pg_temp_%'
        AND schema_name NOT LIKE 'pg_toast_temp_%'
        AND ($1::text IS NULL OR schema_name ILIKE '%' || $1::text || '%')
        AND ($2::text IS NULL OR owner ILIKE '%' || $2::text || '%')
    ORDER BY schema_name
    LIMIT COALESCE($3::int, NULL);
`

func init() {
	if !tools.Register(kind, newConfig) {
		panic(fmt.Sprintf("tool kind %q already registered", kind))
	}
}

func newConfig(ctx context.Context, name string, decoder *yaml.Decoder) (tools.ToolConfig, error) {
	actual := Config{Name: name}
	if err := decoder.DecodeContext(ctx, &actual); err != nil {
		return nil, err
	}
	return actual, nil
}

type compatibleSource interface {
	PostgresPool() *pgxpool.Pool
	RunSQL(context.Context, string, []any) (any, error)
}

type Config struct {
	Name         string   `yaml:"name" validate:"required"`
	Kind         string   `yaml:"kind" validate:"required"`
	Source       string   `yaml:"source" validate:"required"`
	Description  string   `yaml:"description"`
	AuthRequired []string `yaml:"authRequired"`
}

// validate interface
var _ tools.ToolConfig = Config{}

func (cfg Config) ToolConfigKind() string {
	return kind
}

func (cfg Config) Initialize(srcs map[string]sources.Source) (tools.Tool, error) {
	allParameters := parameters.Parameters{
		parameters.NewStringParameterWithDefault("schema_name", "", "Optional: A specific schema name pattern to search for."),
		parameters.NewStringParameterWithDefault("owner", "", "Optional: A specific schema owner name pattern to search for."),
		parameters.NewIntParameterWithDefault("limit", 10, "Optional: The maximum number of schemas to return."),
	}

	if cfg.Description == "" {
		cfg.Description = "Lists all schemas in the database ordered by schema name and excluding system and temporary schemas. It returns the schema name, schema owner, grants, number of functions, number of tables and number of views within each schema."
	}
	mcpManifest := tools.GetMcpManifest(cfg.Name, cfg.Description, cfg.AuthRequired, allParameters, nil)

	// finish tool setup
	return Tool{
		Config:    cfg,
		allParams: allParameters,
		manifest: tools.Manifest{
			Description:  cfg.Description,
			Parameters:   allParameters.Manifest(),
			AuthRequired: cfg.AuthRequired,
		},
		mcpManifest: mcpManifest,
	}, nil
}

// validate interface
var _ tools.Tool = Tool{}

type Tool struct {
	Config
	allParams   parameters.Parameters `yaml:"allParams"`
	manifest    tools.Manifest
	mcpManifest tools.McpManifest
}

func (t Tool) Invoke(ctx context.Context, resourceMgr tools.SourceProvider, params parameters.ParamValues, accessToken tools.AccessToken) (any, error) {
	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Kind)
	if err != nil {
		return nil, err
	}

	paramsMap := params.AsMap()

	newParams, err := parameters.GetParams(t.allParams, paramsMap)
	if err != nil {
		return nil, fmt.Errorf("unable to extract standard params %w", err)
	}
	sliceParams := newParams.AsSlice()
	return source.RunSQL(ctx, listSchemasStatement, sliceParams)
}

func (t Tool) ParseParams(data map[string]any, claims map[string]map[string]any) (parameters.ParamValues, error) {
	return parameters.ParseParams(t.allParams, data, claims)
}

func (t Tool) Manifest() tools.Manifest {
	return t.manifest
}

func (t Tool) McpManifest() tools.McpManifest {
	return t.mcpManifest
}

func (t Tool) Authorized(verifiedAuthServices []string) bool {
	return tools.IsAuthorized(t.AuthRequired, verifiedAuthServices)
}

func (t Tool) RequiresClientAuthorization(resourceMgr tools.SourceProvider) (bool, error) {
	return false, nil
}

func (t Tool) ToConfig() tools.ToolConfig {
	return t.Config
}

func (t Tool) GetAuthTokenHeaderName(resourceMgr tools.SourceProvider) (string, error) {
	return "Authorization", nil
}
