// SPDX-License-Identifier: AGPL-3.0-or-later

// Package database manages the SQLite connection, PRAGMAs, and schema migrations.
package database

import (
	"database/sql"
	"embed"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"sort"
	"strings"

	_ "modernc.org/sqlite"
)

//go:embed migrations/*.sql
var migrationsFS embed.FS

// Open creates a new SQLite database connection with recommended PRAGMAs
// for WAL mode, foreign keys, and performance tuning.
func Open(dbPath string) (*sql.DB, error) {
	// Ensure the directory for the database file exists.
	dir := filepath.Dir(dbPath)
	if err := os.MkdirAll(dir, 0750); err != nil {
		return nil, fmt.Errorf("create db directory: %w", err)
	}

	db, err := sql.Open("sqlite", dbPath)
	if err != nil {
		return nil, fmt.Errorf("open sqlite: %w", err)
	}

	// Apply recommended PRAGMAs. These must be set per-connection, and since
	// database/sql may open multiple connections, we use ConnInitHook via DSN
	// parameters where possible. However, journal_mode persists at the db level.
	pragmas := []string{
		"PRAGMA journal_mode = WAL",
		"PRAGMA busy_timeout = 5000",
		"PRAGMA synchronous = NORMAL",
		"PRAGMA foreign_keys = ON",
		"PRAGMA cache_size = -20000",
	}
	for _, p := range pragmas {
		if _, err := db.Exec(p); err != nil {
			db.Close()
			return nil, fmt.Errorf("set pragma %q: %w", p, err)
		}
	}

	// SQLite works best with a single writer connection.
	db.SetMaxOpenConns(1)

	slog.Info("database opened", "path", dbPath)
	return db, nil
}

// Migrate runs all pending SQL migrations in order. Migrations are embedded
// SQL files named with a numeric prefix (e.g. 001_initial.sql). Each migration
// runs within a transaction.
func Migrate(db *sql.DB) error {
	// Create the migrations tracking table if it doesn't exist.
	_, err := db.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
		version TEXT PRIMARY KEY,
		applied_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
	)`)
	if err != nil {
		return fmt.Errorf("create schema_migrations table: %w", err)
	}

	// Read all migration files.
	entries, err := migrationsFS.ReadDir("migrations")
	if err != nil {
		return fmt.Errorf("read migrations dir: %w", err)
	}

	// Sort by filename to ensure correct order.
	sort.Slice(entries, func(i, j int) bool {
		return entries[i].Name() < entries[j].Name()
	})

	for _, entry := range entries {
		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".sql") {
			continue
		}

		name := entry.Name()

		// Check if this migration has already been applied.
		var count int
		if err := db.QueryRow("SELECT COUNT(*) FROM schema_migrations WHERE version = ?", name).Scan(&count); err != nil {
			return fmt.Errorf("check migration %s: %w", name, err)
		}
		if count > 0 {
			continue
		}

		// Read and execute the migration in a transaction.
		content, err := migrationsFS.ReadFile("migrations/" + name)
		if err != nil {
			return fmt.Errorf("read migration %s: %w", name, err)
		}

		tx, err := db.Begin()
		if err != nil {
			return fmt.Errorf("begin tx for %s: %w", name, err)
		}

		if _, err := tx.Exec(string(content)); err != nil {
			tx.Rollback()
			return fmt.Errorf("execute migration %s: %w", name, err)
		}

		if _, err := tx.Exec("INSERT INTO schema_migrations (version) VALUES (?)", name); err != nil {
			tx.Rollback()
			return fmt.Errorf("record migration %s: %w", name, err)
		}

		if err := tx.Commit(); err != nil {
			return fmt.Errorf("commit migration %s: %w", name, err)
		}

		slog.Info("applied migration", "version", name)
	}

	return nil
}