package query

import (
	"context"
	"database/sql"
	"fmt"
	"time"

	"ai-workflow-skill/packages/coord-core/store"
)

type ReadService struct {
	db    *sql.DB
	orch  *store.OrchStore
	inbox *store.InboxStore
}

type RunListItem struct {
	Run        store.Run      `json:"run"`
	TaskCounts map[string]int `json:"task_counts"`
	TotalTasks int            `json:"total_tasks"`
}

type RunDetail struct {
	Run          store.Run           `json:"run"`
	TaskCounts   map[string]int      `json:"task_counts"`
	TotalTasks   int                 `json:"total_tasks"`
	Tasks        []store.Task        `json:"tasks"`
	BlockedTasks []store.BlockedTask `json:"blocked_tasks"`
}

func NewReadService(db *sql.DB) *ReadService {
	return &ReadService{
		db:    db,
		orch:  store.NewOrchStore(db),
		inbox: store.NewInboxStore(db),
	}
}

func (s *ReadService) ListRuns(ctx context.Context) ([]RunListItem, error) {
	rows, err := s.db.QueryContext(
		ctx,
		`SELECT run_id, goal, summary, status, created_at, updated_at
		 FROM runs
		 ORDER BY updated_at DESC, created_at DESC`,
	)
	if err != nil {
		return nil, fmt.Errorf("query runs: %w", err)
	}
	defer rows.Close()

	var runs []store.Run
	runIDs := make([]string, 0)
	for rows.Next() {
		var (
			run                store.Run
			createdAt, updated string
		)
		if err := rows.Scan(
			&run.RunID,
			&run.Goal,
			&run.Summary,
			&run.Status,
			&createdAt,
			&updated,
		); err != nil {
			return nil, fmt.Errorf("scan run list row: %w", err)
		}

		run.CreatedAt = parseRFC3339(createdAt)
		run.UpdatedAt = parseRFC3339(updated)
		runs = append(runs, run)
		runIDs = append(runIDs, run.RunID)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterate runs: %w", err)
	}

	countsByRunID, err := s.collectTaskCounts(ctx, runIDs)
	if err != nil {
		return nil, err
	}

	items := make([]RunListItem, 0, len(runs))
	for _, run := range runs {
		taskCounts := countsByRunID[run.RunID]
		if taskCounts == nil {
			taskCounts = map[string]int{}
		}

		items = append(items, RunListItem{
			Run:        run,
			TaskCounts: taskCounts,
			TotalTasks: totalTasks(taskCounts),
		})
	}

	return items, nil
}

func (s *ReadService) GetRunDetail(ctx context.Context, runID string) (RunDetail, error) {
	overview, err := s.orch.GetRunOverview(ctx, runID)
	if err != nil {
		return RunDetail{}, err
	}

	blocked, err := s.orch.ListBlockedTasks(ctx, runID)
	if err != nil {
		return RunDetail{}, err
	}

	return RunDetail{
		Run:          overview.Run,
		TaskCounts:   overview.TaskCounts,
		TotalTasks:   totalTasks(overview.TaskCounts),
		Tasks:        overview.Tasks,
		BlockedTasks: blocked,
	}, nil
}

func (s *ReadService) ListRunTasks(ctx context.Context, runID string) ([]store.Task, error) {
	detail, err := s.GetRunDetail(ctx, runID)
	if err != nil {
		return nil, err
	}
	return detail.Tasks, nil
}

func (s *ReadService) ListBlockedTasks(ctx context.Context, runID string) ([]store.BlockedTask, error) {
	return s.orch.ListBlockedTasks(ctx, runID)
}

func (s *ReadService) GetThreadDetail(ctx context.Context, threadID string) (store.ThreadDetail, error) {
	return s.inbox.GetThread(ctx, threadID)
}

func (s *ReadService) collectTaskCounts(ctx context.Context, runIDs []string) (map[string]map[string]int, error) {
	result := make(map[string]map[string]int, len(runIDs))
	if len(runIDs) == 0 {
		return result, nil
	}

	args := make([]any, 0, len(runIDs))
	for _, runID := range runIDs {
		args = append(args, runID)
	}

	rows, err := s.db.QueryContext(
		ctx,
		`SELECT run_id, status, COUNT(*)
		 FROM tasks
		 WHERE run_id IN (`+placeholders(len(runIDs))+`)
		 GROUP BY run_id, status`,
		args...,
	)
	if err != nil {
		return nil, fmt.Errorf("query task counts for runs: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var (
			runID  string
			status string
			count  int
		)
		if err := rows.Scan(&runID, &status, &count); err != nil {
			return nil, fmt.Errorf("scan run task count: %w", err)
		}
		if result[runID] == nil {
			result[runID] = make(map[string]int)
		}
		result[runID][status] = count
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("iterate run task counts: %w", err)
	}

	return result, nil
}

func totalTasks(counts map[string]int) int {
	total := 0
	for _, count := range counts {
		total += count
	}
	return total
}

func placeholders(count int) string {
	if count <= 0 {
		return ""
	}

	buf := make([]byte, 0, count*2-1)
	for i := 0; i < count; i++ {
		if i > 0 {
			buf = append(buf, ',')
		}
		buf = append(buf, '?')
	}
	return string(buf)
}

func parseRFC3339(value string) time.Time {
	parsed, err := time.Parse(time.RFC3339Nano, value)
	if err != nil {
		return time.Time{}
	}
	return parsed
}