package database

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

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

// DB wraps sql.DB with migration support.
type DB struct {
	conn *sql.DB
}

// New opens a SQLite database at dbPath and runs schema migrations.
func New(dbPath string) (*DB, error) {
	conn, err := sql.Open("sqlite3", dbPath)
	if err != nil {
		return nil, fmt.Errorf("open database: %w", err)
	}

	// Enable WAL mode for better concurrent read performance.
	if _, err := conn.Exec("PRAGMA journal_mode=WAL"); err != nil {
		conn.Close()
		return nil, fmt.Errorf("set WAL mode: %w", err)
	}

	db := &DB{conn: conn}
	if err := db.migrate(); err != nil {
		conn.Close()
		return nil, fmt.Errorf("migrate: %w", err)
	}

	return db, nil
}

// Close closes the database connection.
func (db *DB) Close() error {
	return db.conn.Close()
}

// Conn returns the underlying sql.DB for use by other packages.
func (db *DB) Conn() *sql.DB {
	return db.conn
}

// migrate runs all pending schema migrations in order.
func (db *DB) migrate() error {
	// Create the migrations tracking table first, unconditionally.
	if _, err := db.conn.Exec(`CREATE TABLE IF NOT EXISTS _migrations (
		version INTEGER PRIMARY KEY,
		name TEXT NOT NULL,
		applied_at DATETIME DEFAULT CURRENT_TIMESTAMP
	);`); err != nil {
		return fmt.Errorf("create migrations table: %w", err)
	}

	migrations := []struct {
		name string
		sql  string
	}{
		{
			name: "001_create_artist_settings",
			sql: `CREATE TABLE IF NOT EXISTS artist_settings (
				id TEXT PRIMARY KEY,
				name TEXT NOT NULL,
				ignore_singles BOOLEAN DEFAULT 0,
				ignore_compilations BOOLEAN DEFAULT 0,
				monitored BOOLEAN DEFAULT 1
			);`,
		},
		{
			name: "002_create_external_releases",
			sql: `CREATE TABLE IF NOT EXISTS external_releases (
				rgid TEXT PRIMARY KEY,
				artist_id TEXT NOT NULL,
				title TEXT NOT NULL,
				type TEXT,
				release_date TEXT,
				is_ignored BOOLEAN DEFAULT 0
			);`,
		},
		{
			name: "003_create_notifications_sent",
			sql: `CREATE TABLE IF NOT EXISTS notifications_sent (
				rgid TEXT NOT NULL,
				sent_at DATETIME DEFAULT CURRENT_TIMESTAMP,
				PRIMARY KEY (rgid, sent_at)
			);`,
		},
	}

	for _, m := range migrations {
		applied, err := db.isMigrationApplied(m.name)
		if err != nil {
			return fmt.Errorf("check migration %s: %w", m.name, err)
		}
		if applied {
			continue
		}

		if _, err := db.conn.Exec(m.sql); err != nil {
			return fmt.Errorf("apply migration %s: %w", m.name, err)
		}

		if err := db.markMigrationApplied(m.name); err != nil {
			return fmt.Errorf("record migration %s: %w", m.name, err)
		}
	}

	return nil
}

// isMigrationApplied checks whether a migration with the given name has already been applied.
func (db *DB) isMigrationApplied(name string) (bool, error) {
	var count int
	err := db.conn.QueryRow("SELECT COUNT(*) FROM _migrations WHERE name = ?", name).Scan(&count)
	if err != nil {
		return false, err
	}
	return count > 0, nil
}

// markMigrationApplied records a migration as applied.
func (db *DB) markMigrationApplied(name string) error {
	_, err := db.conn.Exec("INSERT INTO _migrations (name) VALUES (?)", name)
	return err
}

// ArtistSettings represents a row in the artist_settings table.
type ArtistSettings struct {
	ID                  string `json:"id"`
	Name                string `json:"name"`
	IgnoreSingles       bool   `json:"ignore_singles"`
	IgnoreCompilations  bool   `json:"ignore_compilations"`
	Monitored           bool   `json:"monitored"`
}

// ExternalRelease represents a row in the external_releases table.
type ExternalRelease struct {
	RGID         string    `json:"rgid"`
	ArtistID     string    `json:"artist_id"`
	Title        string    `json:"title"`
	Type         string    `json:"type"`
	ReleaseDate  string    `json:"release_date"`
	IsIgnored    bool      `json:"is_ignored"`
}

// NotificationSent represents a row in the notifications_sent table.
type NotificationSent struct {
	RGID    string    `json:"rgid"`
	SentAt  time.Time `json:"sent_at"`
}