package database

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

type migration struct {
	version int
	apply   func(context.Context, *sql.Tx) error
}

var migrations = []migration{
	{version: 1, apply: migrationOne},
}

func migrate(ctx context.Context, db *sql.DB) error {
	if _, err := db.ExecContext(ctx, `CREATE TABLE IF NOT EXISTS schema_migrations (
		version INTEGER PRIMARY KEY,
		applied_at TEXT NOT NULL
	)`); err != nil {
		return fmt.Errorf("create migrations table: %w", err)
	}

	for _, m := range migrations {
		var exists int
		if err := db.QueryRowContext(ctx, "SELECT COUNT(*) FROM schema_migrations WHERE version = ?", m.version).Scan(&exists); err != nil {
			return fmt.Errorf("read migration %d: %w", m.version, err)
		}
		if exists != 0 {
			continue
		}

		tx, err := db.BeginTx(ctx, nil)
		if err != nil {
			return fmt.Errorf("begin migration %d: %w", m.version, err)
		}
		if err := m.apply(ctx, tx); err != nil {
			_ = tx.Rollback()
			return fmt.Errorf("apply migration %d: %w", m.version, err)
		}
		if _, err := tx.ExecContext(ctx, "INSERT INTO schema_migrations (version, applied_at) VALUES (?, ?)", m.version, time.Now().UTC().Format(time.RFC3339Nano)); err != nil {
			_ = tx.Rollback()
			return fmt.Errorf("record migration %d: %w", m.version, err)
		}
		if err := tx.Commit(); err != nil {
			return fmt.Errorf("commit migration %d: %w", m.version, err)
		}
	}
	return nil
}

func migrationOne(ctx context.Context, tx *sql.Tx) error {
	statements := []string{
		`CREATE TABLE lists (
			id INTEGER PRIMARY KEY,
			name TEXT NOT NULL CHECK (length(trim(name)) BETWEEN 1 AND 120),
			position REAL NOT NULL
		)`,
		`CREATE TABLE cards (
			id INTEGER PRIMARY KEY,
			list_id INTEGER NOT NULL,
			title TEXT NOT NULL CHECK (length(trim(title)) BETWEEN 1 AND 240),
			description TEXT NOT NULL DEFAULT '',
			position REAL NOT NULL,
			done INTEGER NOT NULL DEFAULT 0 CHECK (done IN (0, 1)),
			created_at TEXT NOT NULL,
			updated_at TEXT NOT NULL,
			FOREIGN KEY (list_id) REFERENCES lists(id) ON DELETE CASCADE
		)`,
		`CREATE INDEX idx_lists_position ON lists(position, id)`,
		`CREATE INDEX idx_cards_list_position ON cards(list_id, position, id)`,
	}
	for _, statement := range statements {
		if _, err := tx.ExecContext(ctx, statement); err != nil {
			return err
		}
	}
	for i, name := range []string{"To do", "In progress", "Done"} {
		if _, err := tx.ExecContext(ctx, "INSERT INTO lists (name, position) VALUES (?, ?)", name, float64(i+1)*1024); err != nil {
			return err
		}
	}
	return nil
}