package app

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgtype"
	"github.com/jackc/pgx/v5/pgxpool"
	"golang.org/x/sync/singleflight"

	"github.com/geo-platform/tenant-api/internal/shared/auditlog"
	"github.com/geo-platform/tenant-api/internal/shared/auth"
	sharedcache "github.com/geo-platform/tenant-api/internal/shared/cache"
	"github.com/geo-platform/tenant-api/internal/shared/middleware"
	"github.com/geo-platform/tenant-api/internal/shared/response"
	sharedschedule "github.com/geo-platform/tenant-api/internal/shared/schedule"
)

type ScheduleTaskService struct {
	pool       *pgxpool.Pool
	auditLogs  *auditlog.AsyncWriter
	cache      sharedcache.Cache
	cacheGroup singleflight.Group
}

func NewScheduleTaskService(pool *pgxpool.Pool, auditLogs *auditlog.AsyncWriter) *ScheduleTaskService {
	return &ScheduleTaskService{pool: pool, auditLogs: auditLogs}
}

func (s *ScheduleTaskService) WithCache(c sharedcache.Cache) *ScheduleTaskService {
	s.cache = c
	return s
}

type ScheduleTaskRequest struct {
	PromptRuleID    int64   `json:"prompt_rule_id" binding:"required"`
	BrandID         *int64  `json:"brand_id"`
	Name            string  `json:"name" binding:"required"`
	CronExpr        string  `json:"cron_expr" binding:"required"`
	TargetPlatform  *string `json:"target_platform"`
	EnableWebSearch *bool   `json:"enable_web_search"`
	GenerateCount   *int    `json:"generate_count"`
	StartAt         *string `json:"start_at"`
	EndAt           *string `json:"end_at"`
}

type ScheduleTaskResponse struct {
	ID              int64   `json:"id"`
	PromptRuleID    int64   `json:"prompt_rule_id"`
	PromptRuleName  *string `json:"prompt_rule_name"`
	BrandID         *int64  `json:"brand_id"`
	BrandName       *string `json:"brand_name"`
	Name            string  `json:"name"`
	CronExpr        string  `json:"cron_expr"`
	TargetPlatform  *string `json:"target_platform"`
	EnableWebSearch bool    `json:"enable_web_search"`
	GenerateCount   int     `json:"generate_count"`
	StartAt         *string `json:"start_at"`
	EndAt           *string `json:"end_at"`
	NextRunAt       *string `json:"next_run_at"`
	Status          string  `json:"status"`
	CreatedAt       string  `json:"created_at"`
	UpdatedAt       string  `json:"updated_at"`
}

type ScheduleTaskListParams struct {
	PromptRuleID *int64  `json:"prompt_rule_id"`
	Status       *string `json:"status"`
	Keyword      *string `json:"keyword"`
	CreatedFrom  *time.Time
	CreatedTo    *time.Time
	Page         int `json:"page"`
	PageSize     int `json:"page_size"`
}

type ScheduleTaskListResponse struct {
	Items []ScheduleTaskResponse `json:"items"`
	Total int64                  `json:"total"`
}

type ScheduleTaskStatusRequest struct {
	Status string `json:"status" binding:"required,oneof=enabled disabled"`
}

func (s *ScheduleTaskService) List(ctx context.Context, params ScheduleTaskListParams) (*ScheduleTaskListResponse, error) {
	actor := auth.MustActor(ctx)
	return sharedcache.LoadJSON(ctx, s.cache, &s.cacheGroup, scheduleTaskListCacheKey(actor.TenantID, params), defaultCacheTTL(), func(loadCtx context.Context) (*ScheduleTaskListResponse, error) {
		return s.loadScheduleTasks(loadCtx, actor.TenantID, params)
	})
}

func (s *ScheduleTaskService) Detail(ctx context.Context, id int64) (*ScheduleTaskResponse, error) {
	actor := auth.MustActor(ctx)
	record, found, err := sharedcache.LoadJSONWithEmpty(ctx, s.cache, &s.cacheGroup, scheduleTaskDetailCacheKey(actor.TenantID, id), defaultCacheTTL(), defaultCacheEmptyTTL(), func(loadCtx context.Context) (*ScheduleTaskResponse, bool, error) {
		return s.loadScheduleTaskDetail(loadCtx, actor.TenantID, id)
	})
	if err != nil {
		return nil, err
	}
	if !found || record == nil {
		return nil, response.ErrNotFound(40432, "schedule_not_found", "schedule task not found")
	}
	return record, nil
}

func (s *ScheduleTaskService) Create(ctx context.Context, req ScheduleTaskRequest) (*ScheduleTaskResponse, error) {
	actor := auth.MustActor(ctx)

	if err := validateScheduleCronExpr(req.CronExpr); err != nil {
		return nil, err
	}
	if err := s.ensurePromptRuleExists(ctx, actor.TenantID, req.PromptRuleID); err != nil {
		return nil, err
	}
	generateCount, err := normalizeScheduleGenerateCount(req.GenerateCount)
	if err != nil {
		return nil, err
	}
	enableWebSearch := boolValue(req.EnableWebSearch)

	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return nil, response.ErrInternal(50010, "create_failed", "failed to begin schedule task transaction")
	}
	defer tx.Rollback(ctx)

	var id int64
	var createdAt time.Time
	var startAt pgtype.Timestamptz
	var endAt pgtype.Timestamptz
	var status string
	err = tx.QueryRow(ctx, `
		INSERT INTO schedule_tasks (
			tenant_id, operator_id, prompt_rule_id, brand_id, name, cron_expr, target_platform,
			enable_web_search, generate_count, start_at, end_at
		)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10::timestamptz, $11::timestamptz)
		RETURNING id, created_at, start_at, end_at, status
	`, actor.TenantID, actor.UserID, req.PromptRuleID, req.BrandID, req.Name, req.CronExpr, req.TargetPlatform, enableWebSearch, generateCount, req.StartAt, req.EndAt).
		Scan(&id, &createdAt, &startAt, &endAt, &status)
	if err != nil {
		return nil, response.ErrInternal(50010, "create_failed", "failed to create schedule task")
	}

	nextRunAt, err := resolveScheduleNextRunForStatus(status, req.CronExpr, timePtrFromTimestamp(startAt), timePtrFromTimestamp(endAt), time.Now())
	if err != nil {
		return nil, response.ErrBadRequest(40015, "invalid_cron_expr", err.Error())
	}
	if _, err := tx.Exec(ctx, `
		UPDATE schedule_tasks
		SET next_run_at = $1,
		    updated_at = NOW()
		WHERE id = $2
		  AND tenant_id = $3
	`, nextRunAt, id, actor.TenantID); err != nil {
		return nil, response.ErrInternal(50010, "create_failed", "failed to initialize next run time")
	}

	if err := tx.Commit(ctx); err != nil {
		return nil, response.ErrInternal(50010, "create_failed", "failed to commit schedule task")
	}

	afterJSON, _ := json.Marshal(map[string]interface{}{
		"id":                id,
		"name":              req.Name,
		"cron_expr":         req.CronExpr,
		"enable_web_search": enableWebSearch,
		"generate_count":    generateCount,
	})
	result := "success"
	resourceType := "schedule_task"
	requestID := middleware.RequestIDFromContext(ctx)
	s.auditLogs.Log(auditlog.Entry{
		OperatorID:   actor.UserID,
		TenantID:     &actor.TenantID,
		Module:       "schedule_task",
		Action:       "create",
		ResourceType: &resourceType,
		ResourceID:   &id,
		RequestID:    nilIfEmptyString(requestID),
		AfterJSON:    afterJSON,
		Result:       &result,
	})

	invalidateScheduleTaskCaches(ctx, s.cache, actor.TenantID, &id)
	return &ScheduleTaskResponse{
		ID: id, PromptRuleID: req.PromptRuleID, BrandID: req.BrandID,
		Name: req.Name, CronExpr: req.CronExpr, TargetPlatform: req.TargetPlatform,
		EnableWebSearch: enableWebSearch, GenerateCount: generateCount,
		Status: status, CreatedAt: fmt.Sprintf("%v", createdAt),
		NextRunAt: timeStringPtr(nextRunAt),
	}, nil
}

func (s *ScheduleTaskService) Update(ctx context.Context, id int64, req ScheduleTaskRequest) error {
	actor := auth.MustActor(ctx)
	if err := validateScheduleCronExpr(req.CronExpr); err != nil {
		return err
	}
	if err := s.ensurePromptRuleExists(ctx, actor.TenantID, req.PromptRuleID); err != nil {
		return err
	}
	generateCount, err := normalizeScheduleGenerateCount(req.GenerateCount)
	if err != nil {
		return err
	}
	enableWebSearch := boolValue(req.EnableWebSearch)

	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return response.ErrInternal(50010, "update_failed", "failed to begin schedule task transaction")
	}
	defer tx.Rollback(ctx)

	var status string
	var startAt pgtype.Timestamptz
	var endAt pgtype.Timestamptz
	err = tx.QueryRow(ctx, `
		UPDATE schedule_tasks SET prompt_rule_id = $1, brand_id = $2, name = $3,
		       cron_expr = $4, target_platform = $5, enable_web_search = $6, generate_count = $7,
		       start_at = $8::timestamptz, end_at = $9::timestamptz, operator_id = $10, updated_at = NOW()
		WHERE id = $11 AND tenant_id = $12 AND deleted_at IS NULL
		RETURNING status, start_at, end_at
	`, req.PromptRuleID, req.BrandID, req.Name, req.CronExpr, req.TargetPlatform, enableWebSearch, generateCount, req.StartAt, req.EndAt, actor.UserID, id, actor.TenantID).
		Scan(&status, &startAt, &endAt)
	if err != nil {
		return response.ErrNotFound(40432, "schedule_not_found", "schedule task not found")
	}

	nextRunAt, err := resolveScheduleNextRunForStatus(status, req.CronExpr, timePtrFromTimestamp(startAt), timePtrFromTimestamp(endAt), time.Now())
	if err != nil {
		return response.ErrBadRequest(40015, "invalid_cron_expr", err.Error())
	}
	if _, err := tx.Exec(ctx, `
		UPDATE schedule_tasks
		SET next_run_at = $1,
		    updated_at = NOW()
		WHERE id = $2
		  AND tenant_id = $3
	`, nextRunAt, id, actor.TenantID); err != nil {
		return response.ErrInternal(50010, "update_failed", "failed to refresh next run time")
	}

	if err := tx.Commit(ctx); err != nil {
		return response.ErrInternal(50010, "update_failed", "failed to commit schedule task")
	}
	invalidateScheduleTaskCaches(ctx, s.cache, actor.TenantID, &id)
	return nil
}

func (s *ScheduleTaskService) Delete(ctx context.Context, id int64) error {
	actor := auth.MustActor(ctx)
	tag, err := s.pool.Exec(ctx, `
		UPDATE schedule_tasks SET deleted_at = NOW(), updated_at = NOW()
		WHERE id = $1 AND tenant_id = $2 AND deleted_at IS NULL
	`, id, actor.TenantID)
	if err != nil || tag.RowsAffected() == 0 {
		return response.ErrNotFound(40432, "schedule_not_found", "schedule task not found")
	}

	afterJSON, _ := json.Marshal(map[string]interface{}{"id": id})
	result := "success"
	resourceType := "schedule_task"
	requestID := middleware.RequestIDFromContext(ctx)
	s.auditLogs.Log(auditlog.Entry{
		OperatorID:   actor.UserID,
		TenantID:     &actor.TenantID,
		Module:       "schedule_task",
		Action:       "delete",
		ResourceType: &resourceType,
		ResourceID:   &id,
		RequestID:    nilIfEmptyString(requestID),
		AfterJSON:    afterJSON,
		Result:       &result,
	})
	invalidateScheduleTaskCaches(ctx, s.cache, actor.TenantID, &id)
	return nil
}

func (s *ScheduleTaskService) ToggleStatus(ctx context.Context, id int64, req ScheduleTaskStatusRequest) error {
	actor := auth.MustActor(ctx)
	tx, err := s.pool.Begin(ctx)
	if err != nil {
		return response.ErrInternal(50010, "update_failed", "failed to begin schedule task transaction")
	}
	defer tx.Rollback(ctx)

	var cronExpr string
	var status string
	var startAt pgtype.Timestamptz
	var endAt pgtype.Timestamptz
	err = tx.QueryRow(ctx, `
		UPDATE schedule_tasks SET status = $1, operator_id = $2, updated_at = NOW()
		WHERE id = $3 AND tenant_id = $4 AND deleted_at IS NULL
		RETURNING cron_expr, status, start_at, end_at
	`, req.Status, actor.UserID, id, actor.TenantID).
		Scan(&cronExpr, &status, &startAt, &endAt)
	if err != nil {
		return response.ErrNotFound(40432, "schedule_not_found", "schedule task not found")
	}

	nextRunAt, err := resolveScheduleNextRunForStatus(status, cronExpr, timePtrFromTimestamp(startAt), timePtrFromTimestamp(endAt), time.Now())
	if err != nil {
		return response.ErrBadRequest(40015, "invalid_cron_expr", err.Error())
	}
	if _, err := tx.Exec(ctx, `
		UPDATE schedule_tasks
		SET next_run_at = $1,
		    updated_at = NOW()
		WHERE id = $2
		  AND tenant_id = $3
	`, nextRunAt, id, actor.TenantID); err != nil {
		return response.ErrInternal(50010, "update_failed", "failed to refresh next run time")
	}

	if err := tx.Commit(ctx); err != nil {
		return response.ErrInternal(50010, "update_failed", "failed to commit schedule task")
	}
	invalidateScheduleTaskCaches(ctx, s.cache, actor.TenantID, &id)
	return nil
}

func (s *ScheduleTaskService) loadScheduleTasks(ctx context.Context, tenantID int64, params ScheduleTaskListParams) (*ScheduleTaskListResponse, error) {
	if params.Page < 1 {
		params.Page = 1
	}
	if params.PageSize < 1 || params.PageSize > 100 {
		params.PageSize = 20
	}
	offset := (params.Page - 1) * params.PageSize

	var total int64
	if err := s.pool.QueryRow(ctx, `
		SELECT COUNT(*) FROM schedule_tasks
		WHERE tenant_id = $1 AND deleted_at IS NULL
		  AND ($2::bigint IS NULL OR prompt_rule_id = $2)
		  AND ($3::text IS NULL OR status = $3)
		  AND ($4::text IS NULL OR name ILIKE '%' || $4 || '%')
		  AND ($5::timestamptz IS NULL OR created_at >= $5)
		  AND ($6::timestamptz IS NULL OR created_at <= $6)
	`, tenantID, params.PromptRuleID, params.Status, params.Keyword, params.CreatedFrom, params.CreatedTo).Scan(&total); err != nil {
		return nil, response.ErrInternal(50010, "count_failed", "failed to count schedule tasks")
	}

	rows, err := s.pool.Query(ctx, `
		SELECT st.id, st.prompt_rule_id, st.brand_id, st.name,
		       st.cron_expr, st.target_platform, st.enable_web_search, st.generate_count, st.start_at, st.end_at,
		       st.next_run_at, st.status, st.created_at, st.updated_at,
		       pr.name AS prompt_rule_name,
		       b.name AS brand_name
		FROM schedule_tasks st
		LEFT JOIN prompt_rules pr ON pr.id = st.prompt_rule_id
		LEFT JOIN brands b ON b.id = st.brand_id
		WHERE st.tenant_id = $1 AND st.deleted_at IS NULL
		  AND ($2::bigint IS NULL OR st.prompt_rule_id = $2)
		  AND ($3::text IS NULL OR st.status = $3)
		  AND ($4::text IS NULL OR st.name ILIKE '%' || $4 || '%')
		  AND ($5::timestamptz IS NULL OR st.created_at >= $5)
		  AND ($6::timestamptz IS NULL OR st.created_at <= $6)
		ORDER BY st.created_at DESC
		LIMIT $7 OFFSET $8
	`, tenantID, params.PromptRuleID, params.Status, params.Keyword, params.CreatedFrom, params.CreatedTo, params.PageSize, offset)
	if err != nil {
		return nil, response.ErrInternal(50010, "query_failed", "failed to list schedule tasks")
	}
	defer rows.Close()

	items := make([]ScheduleTaskResponse, 0)
	for rows.Next() {
		item, err := scanScheduleTaskResponse(rows)
		if err != nil {
			return nil, err
		}
		items = append(items, item)
	}
	return &ScheduleTaskListResponse{Items: items, Total: total}, nil
}

func (s *ScheduleTaskService) loadScheduleTaskDetail(ctx context.Context, tenantID, taskID int64) (*ScheduleTaskResponse, bool, error) {
	row := s.pool.QueryRow(ctx, `
		SELECT st.id, st.prompt_rule_id, st.brand_id, st.name,
		       st.cron_expr, st.target_platform, st.enable_web_search, st.generate_count, st.start_at, st.end_at,
		       st.next_run_at, st.status, st.created_at, st.updated_at,
		       pr.name AS prompt_rule_name,
		       b.name AS brand_name
		FROM schedule_tasks st
		LEFT JOIN prompt_rules pr ON pr.id = st.prompt_rule_id
		LEFT JOIN brands b ON b.id = st.brand_id
		WHERE st.id = $1 AND st.tenant_id = $2 AND st.deleted_at IS NULL
	`, taskID, tenantID)
	item, err := scanScheduleTaskResponse(row)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, false, nil
		}
		return nil, false, err
	}
	return &item, true, nil
}

func scanScheduleTaskResponse(scanner interface {
	Scan(dest ...interface{}) error
}) (ScheduleTaskResponse, error) {
	var item ScheduleTaskResponse
	var createdAt interface{}
	var updatedAt interface{}
	var startAt interface{}
	var endAt interface{}
	var nextRunAt interface{}
	if err := scanner.Scan(&item.ID, &item.PromptRuleID, &item.BrandID, &item.Name,
		&item.CronExpr, &item.TargetPlatform, &item.EnableWebSearch, &item.GenerateCount, &startAt, &endAt,
		&nextRunAt, &item.Status, &createdAt, &updatedAt,
		&item.PromptRuleName, &item.BrandName); err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return ScheduleTaskResponse{}, pgx.ErrNoRows
		}
		return ScheduleTaskResponse{}, response.ErrInternal(50010, "scan_failed", err.Error())
	}
	item.CreatedAt = fmt.Sprintf("%v", createdAt)
	item.UpdatedAt = fmt.Sprintf("%v", updatedAt)
	if startAt != nil {
		value := fmt.Sprintf("%v", startAt)
		item.StartAt = &value
	}
	if endAt != nil {
		value := fmt.Sprintf("%v", endAt)
		item.EndAt = &value
	}
	if nextRunAt != nil {
		value := fmt.Sprintf("%v", nextRunAt)
		item.NextRunAt = &value
	}
	return item, nil
}

func (s *ScheduleTaskService) ensurePromptRuleExists(ctx context.Context, tenantID, promptRuleID int64) error {
	var exists bool
	_ = s.pool.QueryRow(ctx, `
		SELECT EXISTS(SELECT 1 FROM prompt_rules WHERE id = $1 AND tenant_id = $2 AND deleted_at IS NULL)
	`, promptRuleID, tenantID).Scan(&exists)
	if !exists {
		return response.ErrBadRequest(40001, "invalid_rule", "prompt rule not found or not active")
	}
	return nil
}

func resolveScheduleNextRunForStatus(status, cronExpr string, startAt, endAt *time.Time, now time.Time) (*time.Time, error) {
	if status != "enabled" {
		return nil, nil
	}
	return sharedschedule.ComputeNextRun(cronExpr, startAt, endAt, now)
}

func validateScheduleCronExpr(cronExpr string) error {
	if _, err := sharedschedule.Parse(cronExpr); err != nil {
		return response.ErrBadRequest(40015, "invalid_cron_expr", err.Error())
	}
	return nil
}

func normalizeScheduleGenerateCount(value *int) (int, error) {
	if value == nil {
		return 1, nil
	}
	if *value < 1 || *value > 20 {
		return 0, response.ErrBadRequest(40022, "invalid_generate_count", "generate_count must be between 1 and 20")
	}
	return *value, nil
}

func boolValue(value *bool) bool {
	return value != nil && *value
}

func timePtrFromTimestamp(value pgtype.Timestamptz) *time.Time {
	if !value.Valid {
		return nil
	}
	result := value.Time.Round(0)
	return &result
}

func timeStringPtr(value *time.Time) *string {
	if value == nil {
		return nil
	}
	text := value.Format(time.RFC3339)
	return &text
}