package sqlite

import (
	"database/sql"
	"dwelling-radio/internal/radio"
	"dwelling-radio/internal/statistics"
	_ "embed"
	"fmt"
	"time"

	_ "github.com/mattn/go-sqlite3"
	"github.com/pkg/errors"
)

const dbDateFormat = "2006-01-02 15:04:05.999"

var (
	//go:embed queries/schema.sql
	querySchema string

	//go:embed queries/song_add.sql
	querySongAdd string

	//go:embed queries/history_add.sql
	queryHistoryAdd string

	//go:embed queries/last_n_songs.sql
	queryLastNSongs string
	//go:embed queries/most_popular_songs.sql
	queryMostPopularSongs string
	//go:embed queries/most_simultaneous_listeners.sql
	queryMostSimultaneousListeners string
)

var (
	stmtSongAdd                   *sql.Stmt
	stmtHistoryAdd                *sql.Stmt
	stmtLastNSongs                *sql.Stmt
	stmtMostPopularSongs          *sql.Stmt
	stmtMostSimultaneousListeners *sql.Stmt
)

type SQLiteStatistics struct {
	db *sql.DB
}

func initDBStatements(db *sql.DB) error {
	db.Exec("PRAGMA foreign_keys = ON;")

	_, err := db.Exec(querySchema)
	if err != nil {
		return errors.Wrap(err, "failed to init schema")
	}

	stmtSongAdd, err = db.Prepare(querySongAdd)
	if err != nil {
		return errors.Wrap(err, "failed to prepare querySongAdd")
	}

	stmtHistoryAdd, err = db.Prepare(queryHistoryAdd)
	if err != nil {
		return errors.Wrap(err, "failed to prepare queryHistoryAdd")
	}

	stmtLastNSongs, err = db.Prepare(queryLastNSongs)
	if err != nil {
		return errors.Wrap(err, "failed to prepare queryLastNSongs")
	}

	stmtMostPopularSongs, err = db.Prepare(queryMostPopularSongs)
	if err != nil {
		return errors.Wrap(err, "failed to prepare queryMostPopularSongs")
	}

	stmtMostSimultaneousListeners, err = db.Prepare(queryMostSimultaneousListeners)
	if err != nil {
		return errors.Wrap(err, "failed to prepare queryMostSimultaneousListeners")
	}

	return nil
}

func New(path string) (statistics.Statistics, error) {
	db, err := sql.Open("sqlite3", fmt.Sprintf("file:%s?_journal=WAL&_mutex=full", path))
	if err != nil {
		return nil, err
	}

	if err := initDBStatements(db); err != nil {
		return nil, err
	}

	return &SQLiteStatistics{db: db}, nil
}

func (s *SQLiteStatistics) Add(song *radio.Song) error {
	if song == nil || song.Artist == "" || song.Title == "" {
		return errors.New("No song or an empty one was passed.")
	}

	tx, err := s.db.Begin()
	if err != nil {
		return err
	}
	defer tx.Rollback()

	row := tx.Stmt(stmtSongAdd).QueryRow(song.Artist, song.Title)
	if row.Err() != nil {
		return row.Err()
	}

	var songID int64
	if err := row.Scan(&songID); err != nil {
		return err
	}

	res, err := tx.Stmt(stmtHistoryAdd).Exec(song.StartAt.UTC().Format(dbDateFormat),
		songID, song.Listeners, song.MaxListeners)
	if err != nil {
		return err
	} else if ra, err := res.RowsAffected(); ra == 0 || err != nil {
		return errors.New("a song wasn't added to history, but there were no errors")
	}

	tx.Commit()

	return nil
}

func (s *SQLiteStatistics) LastNSongs(n int64) ([]radio.Song, error) {
	if n == 0 {
		return nil, nil
	}

	tx, err := s.db.Begin()
	if err != nil {
		return nil, err
	}
	defer tx.Rollback()

	rows, err := tx.Stmt(stmtLastNSongs).Query(n)
	if err != nil {
		return nil, err
	}

	songs := make([]radio.Song, n)

	i := 0
	for rows.Next() {
		var startAt string

		if err := rows.Scan(&startAt, &songs[i].Artist, &songs[i].Title,
			&songs[i].Listeners, &songs[i].MaxListeners); err != nil {
			return nil, err
		}

		songs[i].StartAt, err = time.Parse(dbDateFormat, startAt)
		if err != nil {
			return nil, err
		}

		i++
	}

	tx.Commit()

	if i == 0 {
		return nil, nil
	}

	lst := make([]radio.Song, i)
	copy(lst, songs[:])

	return lst, nil
}

func (s *SQLiteStatistics) MostNPopularSongs(n int64) ([]radio.Song, error) {
	if n == 0 {
		return nil, nil
	}

	return nil, nil
}

func (s *SQLiteStatistics) MostSimultaneousListeners() (radio.Song, error) {
	return radio.Song{}, nil
}

func (s *SQLiteStatistics) Close() error {
	return s.db.Close()
}