// Package progress stores and retrieves per-user playback/reading position.
//
// One table, one shape, every media kind: milliseconds for audio and video, a
// spine index or page number for text. Callers that don't fit the integer
// model should encode their position into it rather than adding a column.
package progress

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

	"github.com/mithral/vellum/internal/core"
)

// ErrNoFile means an item has no media_files row to attach progress to.
var ErrNoFile = errors.New("progress: item has no file to track")

// Progress is one user's position in one item's file.
type Progress struct {
	ItemID    int64     `json:"item_id"`
	FileID    int64     `json:"file_id"`
	Kind      string    `json:"kind"`
	Position  int64     `json:"position"`
	Duration  int64     `json:"duration"`
	Percent   float64   `json:"percent"`
	Finished  bool      `json:"finished"`
	UpdatedAt time.Time `json:"updated_at"`
}

// Get returns the most recently updated progress row for a user and item.
// The second return value is false when the user has never touched the item.
func Get(ctx context.Context, db *sql.DB, userID, itemID int64) (Progress, bool, error) {
	var (
		p         Progress
		finished  int
		updatedAt string
	)
	err := db.QueryRowContext(ctx, `
		SELECT item_id, file_id, kind, position, duration, percent, finished, updated_at
		FROM progress
		WHERE user_id = ? AND item_id = ?
		ORDER BY updated_at DESC
		LIMIT 1`, userID, itemID,
	).Scan(&p.ItemID, &p.FileID, &p.Kind, &p.Position, &p.Duration, &p.Percent, &finished, &updatedAt)
	if errors.Is(err, sql.ErrNoRows) {
		return Progress{}, false, nil
	}
	if err != nil {
		return Progress{}, false, fmt.Errorf("progress: get: %w", err)
	}
	p.Finished = finished == 1
	p.UpdatedAt, _ = time.Parse(time.RFC3339Nano, updatedAt)
	return p, true, nil
}

// Put upserts progress. A zero FileID resolves to the item's first file, which
// is what single-file items (epub, cbz) always are.
func Put(ctx context.Context, db *sql.DB, userID int64, p Progress) (Progress, error) {
	if p.FileID == 0 {
		fileID, err := firstFileID(ctx, db, p.ItemID)
		if err != nil {
			return Progress{}, err
		}
		p.FileID = fileID
	}
	if p.Kind == "" {
		_ = db.QueryRowContext(ctx, `SELECT kind FROM media_items WHERE id = ?`, p.ItemID).Scan(&p.Kind)
	}

	if p.Percent < 0 {
		p.Percent = 0
	}
	if p.Percent > 1 {
		p.Percent = 1
	}
	// A timed item at 100% is finished even if the client did not say so.
	if p.Duration > 0 && p.Position >= p.Duration {
		p.Percent = 1
		p.Finished = true
	}

	now := time.Now().UTC()
	_, err := db.ExecContext(ctx, `
		INSERT INTO progress (user_id, item_id, file_id, kind, position, duration, percent, finished, updated_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
		ON CONFLICT (user_id, item_id, file_id)
		DO UPDATE SET kind = excluded.kind, position = excluded.position,
		              duration = excluded.duration, percent = excluded.percent,
		              finished = excluded.finished, updated_at = excluded.updated_at`,
		userID, p.ItemID, p.FileID, p.Kind, p.Position, p.Duration, p.Percent, boolInt(p.Finished),
		core.Stamp(now))
	if err != nil {
		return Progress{}, fmt.Errorf("progress: put: %w", err)
	}
	p.UpdatedAt = now
	return p, nil
}

// Delete clears progress for a user and item.
func Delete(ctx context.Context, db *sql.DB, userID, itemID int64) error {
	_, err := db.ExecContext(ctx, `DELETE FROM progress WHERE user_id = ? AND item_id = ?`, userID, itemID)
	return err
}

// RecentlyUpdated powers a "Continue reading/watching" shelf.
func RecentlyUpdated(ctx context.Context, db *sql.DB, userID int64, limit int) ([]Progress, error) {
	if limit <= 0 || limit > 200 {
		limit = 20
	}
	rows, err := db.QueryContext(ctx, `
		SELECT item_id, file_id, kind, position, duration, percent, finished, updated_at
		FROM progress
		WHERE user_id = ? AND finished = 0
		ORDER BY updated_at DESC
		LIMIT ?`, userID, limit)
	if err != nil {
		return nil, fmt.Errorf("progress: recent: %w", err)
	}
	defer rows.Close()

	out := []Progress{}
	for rows.Next() {
		var p Progress
		var finished int
		var updatedAt string
		if err := rows.Scan(&p.ItemID, &p.FileID, &p.Kind, &p.Position, &p.Duration, &p.Percent, &finished, &updatedAt); err != nil {
			return nil, err
		}
		p.Finished = finished == 1
		p.UpdatedAt, _ = time.Parse(time.RFC3339Nano, updatedAt)
		out = append(out, p)
	}
	return out, rows.Err()
}

func firstFileID(ctx context.Context, db *sql.DB, itemID int64) (int64, error) {
	var id int64
	err := db.QueryRowContext(ctx,
		`SELECT id FROM media_files WHERE item_id = ? ORDER BY id LIMIT 1`, itemID).Scan(&id)
	if errors.Is(err, sql.ErrNoRows) {
		return 0, ErrNoFile
	}
	if err != nil {
		return 0, fmt.Errorf("progress: first file: %w", err)
	}
	return id, nil
}

func boolInt(b bool) int {
	if b {
		return 1
	}
	return 0
}