// 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 bigqueryforecast

import (
	"context"
	"fmt"
	"strings"

	bigqueryapi "cloud.google.com/go/bigquery"
	yaml "github.com/goccy/go-yaml"
	"github.com/googleapis/genai-toolbox/internal/sources"
	bigqueryds "github.com/googleapis/genai-toolbox/internal/sources/bigquery"
	"github.com/googleapis/genai-toolbox/internal/tools"
	bqutil "github.com/googleapis/genai-toolbox/internal/tools/bigquery/bigquerycommon"
	"github.com/googleapis/genai-toolbox/internal/util"
	"github.com/googleapis/genai-toolbox/internal/util/parameters"
	bigqueryrestapi "google.golang.org/api/bigquery/v2"
)

const kind string = "bigquery-forecast"

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 {
	BigQueryClient() *bigqueryapi.Client
	UseClientAuthorization() bool
	IsDatasetAllowed(projectID, datasetID string) bool
	BigQueryAllowedDatasets() []string
	BigQuerySession() bigqueryds.BigQuerySessionProvider
	RetrieveClientAndService(tools.AccessToken) (*bigqueryapi.Client, *bigqueryrestapi.Service, error)
	RunSQL(context.Context, *bigqueryapi.Client, string, string, []bigqueryapi.QueryParameter, []*bigqueryapi.ConnectionProperty) (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" validate:"required"`
	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) {
	// verify source exists
	rawS, ok := srcs[cfg.Source]
	if !ok {
		return nil, fmt.Errorf("no source named %q configured", cfg.Source)
	}

	// verify the source is compatible
	s, ok := rawS.(compatibleSource)
	if !ok {
		return nil, fmt.Errorf("invalid source for %q tool: source %q not compatible", kind, cfg.Source)
	}

	allowedDatasets := s.BigQueryAllowedDatasets()
	historyDataDescription := "The table id or the query of the history time series data."
	if len(allowedDatasets) > 0 {
		datasetIDs := []string{}
		for _, ds := range allowedDatasets {
			datasetIDs = append(datasetIDs, fmt.Sprintf("`%s`", ds))
		}
		historyDataDescription += fmt.Sprintf(" The query or table must only access datasets from the following list: %s.", strings.Join(datasetIDs, ", "))
	}

	historyDataParameter := parameters.NewStringParameter("history_data", historyDataDescription)
	timestampColumnNameParameter := parameters.NewStringParameter("timestamp_col",
		"The name of the time series timestamp column.")
	dataColumnNameParameter := parameters.NewStringParameter("data_col",
		"The name of the time series data column.")
	idColumnNameParameter := parameters.NewArrayParameterWithDefault("id_cols", []any{},
		"An array of the time series id column names.",
		parameters.NewStringParameter("id_col", "The name of time series id column."))
	horizonParameter := parameters.NewIntParameterWithDefault("horizon", 10, "The number of forecasting steps.")
	params := parameters.Parameters{historyDataParameter,
		timestampColumnNameParameter, dataColumnNameParameter, idColumnNameParameter, horizonParameter}

	mcpManifest := tools.GetMcpManifest(cfg.Name, cfg.Description, cfg.AuthRequired, params, nil)

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

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

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

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

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()
	historyData, ok := paramsMap["history_data"].(string)
	if !ok {
		return nil, fmt.Errorf("unable to cast history_data parameter %v", paramsMap["history_data"])
	}
	timestampCol, ok := paramsMap["timestamp_col"].(string)
	if !ok {
		return nil, fmt.Errorf("unable to cast timestamp_col parameter %v", paramsMap["timestamp_col"])
	}
	dataCol, ok := paramsMap["data_col"].(string)
	if !ok {
		return nil, fmt.Errorf("unable to cast data_col parameter %v", paramsMap["data_col"])
	}
	idColsRaw, ok := paramsMap["id_cols"].([]any)
	if !ok {
		return nil, fmt.Errorf("unable to cast id_cols parameter %v", paramsMap["id_cols"])
	}
	var idCols []string
	for _, v := range idColsRaw {
		s, ok := v.(string)
		if !ok {
			return nil, fmt.Errorf("id_cols contains non-string value: %v", v)
		}
		idCols = append(idCols, s)
	}
	horizon, ok := paramsMap["horizon"].(int)
	if !ok {
		if h, ok := paramsMap["horizon"].(float64); ok {
			horizon = int(h)
		} else {
			return nil, fmt.Errorf("unable to cast horizon parameter %v", paramsMap["horizon"])
		}
	}

	bqClient, restService, err := source.RetrieveClientAndService(accessToken)
	if err != nil {
		return nil, err
	}

	var historyDataSource string
	trimmedUpperHistoryData := strings.TrimSpace(strings.ToUpper(historyData))
	if strings.HasPrefix(trimmedUpperHistoryData, "SELECT") || strings.HasPrefix(trimmedUpperHistoryData, "WITH") {
		if len(source.BigQueryAllowedDatasets()) > 0 {
			var connProps []*bigqueryapi.ConnectionProperty
			session, err := source.BigQuerySession()(ctx)
			if err != nil {
				return nil, fmt.Errorf("failed to get BigQuery session: %w", err)
			}
			if session != nil {
				connProps = []*bigqueryapi.ConnectionProperty{
					{Key: "session_id", Value: session.ID},
				}
			}
			dryRunJob, err := bqutil.DryRunQuery(ctx, restService, source.BigQueryClient().Project(), source.BigQueryClient().Location, historyData, nil, connProps)
			if err != nil {
				return nil, fmt.Errorf("query validation failed: %w", err)
			}
			statementType := dryRunJob.Statistics.Query.StatementType
			if statementType != "SELECT" {
				return nil, fmt.Errorf("the 'history_data' parameter only supports a table ID or a SELECT query. The provided query has statement type '%s'", statementType)
			}

			queryStats := dryRunJob.Statistics.Query
			if queryStats != nil {
				for _, tableRef := range queryStats.ReferencedTables {
					if !source.IsDatasetAllowed(tableRef.ProjectId, tableRef.DatasetId) {
						return nil, fmt.Errorf("query in history_data accesses dataset '%s.%s', which is not in the allowed list", tableRef.ProjectId, tableRef.DatasetId)
					}
				}
			} else {
				return nil, fmt.Errorf("could not analyze query in history_data to validate against allowed datasets")
			}
		}
		historyDataSource = fmt.Sprintf("(%s)", historyData)
	} else {
		if len(source.BigQueryAllowedDatasets()) > 0 {
			parts := strings.Split(historyData, ".")
			var projectID, datasetID string

			switch len(parts) {
			case 3: // project.dataset.table
				projectID = parts[0]
				datasetID = parts[1]
			case 2: // dataset.table
				projectID = source.BigQueryClient().Project()
				datasetID = parts[0]
			default:
				return nil, fmt.Errorf("invalid table ID format for 'history_data': %q. Expected 'dataset.table' or 'project.dataset.table'", historyData)
			}

			if !source.IsDatasetAllowed(projectID, datasetID) {
				return nil, fmt.Errorf("access to dataset '%s.%s' (from table '%s') is not allowed", projectID, datasetID, historyData)
			}
		}
		historyDataSource = fmt.Sprintf("TABLE `%s`", historyData)
	}

	idColsArg := ""
	if len(idCols) > 0 {
		idColsFormatted := fmt.Sprintf("['%s']", strings.Join(idCols, "', '"))
		idColsArg = fmt.Sprintf(", id_cols => %s", idColsFormatted)
	}
	sql := fmt.Sprintf(`SELECT * 
		FROM AI.FORECAST(
			%s,
			data_col => '%s',
			timestamp_col => '%s',
			horizon => %d%s)`,
		historyDataSource, dataCol, timestampCol, horizon, idColsArg)

	session, err := source.BigQuerySession()(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed to get BigQuery session: %w", err)
	}
	var connProps []*bigqueryapi.ConnectionProperty
	if session != nil {
		// Add session ID to the connection properties for subsequent calls.
		connProps = []*bigqueryapi.ConnectionProperty{
			{Key: "session_id", Value: session.ID},
		}
	}

	// Log the query executed for debugging.
	logger, err := util.LoggerFromContext(ctx)
	if err != nil {
		return nil, fmt.Errorf("error getting logger: %s", err)
	}
	logger.DebugContext(ctx, fmt.Sprintf("executing `%s` tool query: %s", kind, sql))

	return source.RunSQL(ctx, bqClient, sql, "SELECT", nil, connProps)
}

func (t Tool) ParseParams(data map[string]any, claims map[string]map[string]any) (parameters.ParamValues, error) {
	return parameters.ParseParams(t.Parameters, 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) {
	source, err := tools.GetCompatibleSource[compatibleSource](resourceMgr, t.Source, t.Name, t.Kind)
	if err != nil {
		return false, err
	}
	return source.UseClientAuthorization(), nil
}

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