package store

import (
	"context"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

var ErrInvalidTransition = errors.New("invalid job status transition")

type Store struct{ pool *pgxpool.Pool }

func New(pool *pgxpool.Pool) *Store { return &Store{pool: pool} }

type Episode struct {
	ID, SeriesID, SeriesTitle, Title, BroadcasterName, ThumbnailPath string
	DurationSeconds                                                  int
	EndAt                                                            *time.Time
}

type Job struct {
	ID                                 int64
	EpisodeID, SeriesID, SeriesTitle   string
	Title, BroadcasterName             string
	DurationSeconds                    int
	EndAt                              *time.Time
	ThumbnailPath, Source, Status      string
	Phase, FormatID                    *string
	DownloadedBytes, TotalBytes        *int64
	TotalIsEstimate                    bool
	SpeedBPS, ETASeconds               *float64
	FragmentIndex, FragmentCount       *int32
	ErrorKind, ErrorMessage, FilePath  *string
	FileSizeBytes                      *int64
	Attempts                           int
	HeartbeatAt, StartedAt, FinishedAt *time.Time
	CreatedAt, UpdatedAt               time.Time
}

type Progress struct {
	Phase           string
	DownloadedBytes *int64
	TotalBytes      *int64
	TotalIsEstimate bool
	SpeedBPS        *float64
	ETASeconds      *float64
	FragmentIndex   *int32
	FragmentCount   *int32
	FormatID        *string
}

type Subscription struct {
	SeriesID, SeriesTitle string
	Enabled               bool
	CreatedAt             time.Time
	LastCheckedAt         *time.Time
}

const jobColumns = `id, episode_id, series_id, series_title, title, broadcaster_name,
	duration_seconds, end_at, thumbnail_path, source, status, phase,
	downloaded_bytes, total_bytes, total_is_estimate, speed_bps, eta_seconds,
	fragment_index, fragment_count, format_id, error_kind, error_message,
	file_path, file_size_bytes, attempts, heartbeat_at, created_at,
	started_at, finished_at, updated_at`

var claimedJobColumns = func() string {
	columns := strings.Split(jobColumns, ",")
	for i, column := range columns {
		columns[i] = "j." + strings.TrimSpace(column)
	}
	return strings.Join(columns, ", ")
}()

func scanJob(row pgx.Row) (Job, error) {
	var j Job
	err := row.Scan(&j.ID, &j.EpisodeID, &j.SeriesID, &j.SeriesTitle, &j.Title,
		&j.BroadcasterName, &j.DurationSeconds, &j.EndAt, &j.ThumbnailPath,
		&j.Source, &j.Status, &j.Phase, &j.DownloadedBytes, &j.TotalBytes,
		&j.TotalIsEstimate, &j.SpeedBPS, &j.ETASeconds, &j.FragmentIndex,
		&j.FragmentCount, &j.FormatID, &j.ErrorKind, &j.ErrorMessage,
		&j.FilePath, &j.FileSizeBytes, &j.Attempts, &j.HeartbeatAt,
		&j.CreatedAt, &j.StartedAt, &j.FinishedAt, &j.UpdatedAt)
	return j, err
}

// Enqueue は同じエピソードの既存ジョブを再利用する。
func (s *Store) Enqueue(ctx context.Context, ep Episode, source string) (Job, bool, error) {
	row := s.pool.QueryRow(ctx, `INSERT INTO download_jobs
		(episode_id, series_id, series_title, title, broadcaster_name, duration_seconds, end_at, thumbnail_path, source)
		VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9) ON CONFLICT (episode_id) DO NOTHING RETURNING `+jobColumns,
		ep.ID, ep.SeriesID, ep.SeriesTitle, ep.Title, ep.BroadcasterName,
		ep.DurationSeconds, ep.EndAt, ep.ThumbnailPath, source)
	job, err := scanJob(row)
	if err == nil {
		return job, true, nil
	}
	if !errors.Is(err, pgx.ErrNoRows) {
		return Job{}, false, err
	}
	job, err = scanJob(s.pool.QueryRow(ctx, `SELECT `+jobColumns+` FROM download_jobs WHERE episode_id=$1`, ep.ID))
	return job, false, err
}

func (s *Store) GetJob(ctx context.Context, id int64) (Job, error) {
	return scanJob(s.pool.QueryRow(ctx, `SELECT `+jobColumns+` FROM download_jobs WHERE id=$1`, id))
}

// Retry は失敗・中断されたジョブの実行時情報を消して再投入する。
func (s *Store) Retry(ctx context.Context, id int64) error {
	tag, err := s.pool.Exec(ctx, `UPDATE download_jobs SET status='queued', phase=NULL,
		downloaded_bytes=NULL, total_bytes=NULL, total_is_estimate=false, speed_bps=NULL,
		eta_seconds=NULL, fragment_index=NULL, fragment_count=NULL, format_id=NULL,
		error_kind=NULL, error_message=NULL, heartbeat_at=NULL, started_at=NULL,
		finished_at=NULL, updated_at=now()
		WHERE id=$1 AND status IN ('failed','canceled')`, id)
	return transitionResult(tag.RowsAffected(), err)
}

// ClaimNext は最も古い未実行ジョブを同時 worker と重複せず取得する。
func (s *Store) ClaimNext(ctx context.Context) (Job, error) {
	return scanJob(s.pool.QueryRow(ctx, `WITH next AS (
		SELECT id FROM download_jobs WHERE status='queued'
		ORDER BY created_at, id LIMIT 1 FOR UPDATE SKIP LOCKED
	) UPDATE download_jobs AS j SET status='running', attempts=j.attempts+1,
		started_at=now(), heartbeat_at=now(), updated_at=now()
		FROM next WHERE j.id=next.id RETURNING `+claimedJobColumns))
}

func (s *Store) UpdateProgress(ctx context.Context, id int64, p Progress) error {
	tag, err := s.pool.Exec(ctx, `UPDATE download_jobs SET phase=$2, downloaded_bytes=$3,
		total_bytes=$4, total_is_estimate=$5, speed_bps=$6, eta_seconds=$7,
		fragment_index=$8, fragment_count=$9, format_id=$10,
		heartbeat_at=now(), updated_at=now() WHERE id=$1 AND status='running'`,
		id, p.Phase, p.DownloadedBytes, p.TotalBytes, p.TotalIsEstimate,
		p.SpeedBPS, p.ETASeconds, p.FragmentIndex, p.FragmentCount, p.FormatID)
	return transitionResult(tag.RowsAffected(), err)
}

func (s *Store) Complete(ctx context.Context, id int64, filePath string, fileSizeBytes int64) error {
	tag, err := s.pool.Exec(ctx, `UPDATE download_jobs SET status='succeeded', phase=NULL,
		file_path=$2, file_size_bytes=$3, heartbeat_at=NULL, finished_at=now(), updated_at=now()
		WHERE id=$1 AND status='running'`, id, filePath, fileSizeBytes)
	return transitionResult(tag.RowsAffected(), err)
}

func (s *Store) Fail(ctx context.Context, id int64, kind, message string) error {
	tag, err := s.pool.Exec(ctx, `UPDATE download_jobs SET status='failed', phase=NULL,
		error_kind=$2, error_message=$3, heartbeat_at=NULL, finished_at=now(), updated_at=now()
		WHERE id=$1 AND status='running'`, id, kind, message)
	return transitionResult(tag.RowsAffected(), err)
}

func (s *Store) Cancel(ctx context.Context, id int64) error {
	tag, err := s.pool.Exec(ctx, `UPDATE download_jobs SET status='canceled', phase=NULL,
		error_kind='canceled', heartbeat_at=NULL, finished_at=now(), updated_at=now()
		WHERE id=$1 AND status IN ('queued','running')`, id)
	return transitionResult(tag.RowsAffected(), err)
}

// RequeueStale は cutoff より前に heartbeat が止まった実行中ジョブを戻す。
func (s *Store) RequeueStale(ctx context.Context, cutoff time.Time) (int64, error) {
	tag, err := s.pool.Exec(ctx, `UPDATE download_jobs SET status='queued', phase=NULL,
		downloaded_bytes=NULL, total_bytes=NULL, total_is_estimate=false, speed_bps=NULL,
		eta_seconds=NULL, fragment_index=NULL, fragment_count=NULL, format_id=NULL,
		heartbeat_at=NULL, started_at=NULL, updated_at=now()
		WHERE status='running' AND heartbeat_at < $1`, cutoff)
	return tag.RowsAffected(), err
}

func transitionResult(count int64, err error) error {
	if err != nil {
		return err
	}
	if count == 0 {
		return ErrInvalidTransition
	}
	return nil
}

// ListJobs は指定状態のジョブを新しい順に返す。空の状態は全件を意味する。
func (s *Store) ListJobs(ctx context.Context, status string, limit int) ([]Job, error) {
	if status != "" && status != "queued" && status != "running" && status != "succeeded" && status != "failed" && status != "canceled" {
		return nil, fmt.Errorf("invalid status: %s", status)
	}
	if limit <= 0 {
		return nil, errors.New("limit must be positive")
	}
	rows, err := s.pool.Query(ctx, `SELECT `+jobColumns+` FROM download_jobs
		WHERE ($1='' OR status=$1) ORDER BY created_at DESC, id DESC LIMIT $2`, status, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var jobs []Job
	for rows.Next() {
		job, err := scanJob(rows)
		if err != nil {
			return nil, err
		}
		jobs = append(jobs, job)
	}
	return jobs, rows.Err()
}

func (s *Store) EpisodeStatuses(ctx context.Context, ids []string) (map[string]string, error) {
	result := make(map[string]string)
	if len(ids) == 0 {
		return result, nil
	}
	rows, err := s.pool.Query(ctx, `SELECT episode_id, status FROM download_jobs WHERE episode_id = ANY($1)`, ids)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	for rows.Next() {
		var id, status string
		if err := rows.Scan(&id, &status); err != nil {
			return nil, err
		}
		result[id] = status
	}
	return result, rows.Err()
}

// AddSubscription は登録済みシリーズのタイトルと有効状態を変更しない。
func (s *Store) AddSubscription(ctx context.Context, seriesID, title string) (bool, error) {
	tag, err := s.pool.Exec(ctx, `INSERT INTO subscriptions (series_id, series_title)
		VALUES ($1,$2) ON CONFLICT (series_id) DO NOTHING`, seriesID, title)
	return tag.RowsAffected() == 1, err
}

func (s *Store) DeleteSubscription(ctx context.Context, seriesID string) (bool, error) {
	tag, err := s.pool.Exec(ctx, `DELETE FROM subscriptions WHERE series_id=$1`, seriesID)
	return tag.RowsAffected() == 1, err
}

func (s *Store) ListSubscriptions(ctx context.Context) ([]Subscription, error) {
	rows, err := s.pool.Query(ctx, `SELECT series_id, series_title, enabled, created_at, last_checked_at
		FROM subscriptions ORDER BY created_at DESC, series_id`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var subs []Subscription
	for rows.Next() {
		var sub Subscription
		if err := rows.Scan(&sub.SeriesID, &sub.SeriesTitle, &sub.Enabled, &sub.CreatedAt, &sub.LastCheckedAt); err != nil {
			return nil, err
		}
		subs = append(subs, sub)
	}
	return subs, rows.Err()
}

func (s *Store) SetSubscriptionChecked(ctx context.Context, seriesID string, checkedAt time.Time) error {
	tag, err := s.pool.Exec(ctx, `UPDATE subscriptions SET last_checked_at=$2 WHERE series_id=$1`, seriesID, checkedAt)
	return transitionResult(tag.RowsAffected(), err)
}