package database

import (
	"context"
	"fmt"
	"runtime"

	"zombiezen.com/go/sqlite"
	"zombiezen.com/go/sqlite/sqlitex"
)

const DefaultPath = "dk.db"

// DB wraps a SQLite connection pool with simplified methods
type DB struct {
	pool *sqlitex.Pool
}

// Open creates a new database connection pool
func Open(path string) (*DB, error) {
	if path == "" {
		path = DefaultPath
	}

	poolSize := max(runtime.GOMAXPROCS(0), 2)

	pool, err := sqlitex.NewPool(path, sqlitex.PoolOptions{
		PoolSize: poolSize,
		Flags:    sqlite.OpenCreate | sqlite.OpenReadWrite | sqlite.OpenWAL,
	})
	if err != nil {
		return nil, fmt.Errorf("failed to open database pool: %w", err)
	}

	conn, err := pool.Take(context.Background())
	if err != nil {
		pool.Close()
		return nil, fmt.Errorf("failed to get connection from pool: %w", err)
	}
	defer pool.Put(conn)

	if err := sqlitex.ExecuteTransient(conn, "PRAGMA journal_mode = WAL", nil); err != nil {
		pool.Close()
		return nil, fmt.Errorf("failed to set WAL mode: %w", err)
	}

	if err := sqlitex.ExecuteTransient(conn, "PRAGMA synchronous = NORMAL", nil); err != nil {
		pool.Close()
		return nil, fmt.Errorf("failed to set synchronous mode: %w", err)
	}

	return &DB{pool: pool}, nil
}

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

// Exec executes a SQL statement without returning results
func (db *DB) Exec(query string, args ...any) error {
	conn, err := db.pool.Take(context.Background())
	if err != nil {
		return fmt.Errorf("failed to get connection from pool: %w", err)
	}
	defer db.pool.Put(conn)

	if len(args) == 0 {
		return sqlitex.ExecuteTransient(conn, query, nil)
	}

	return sqlitex.ExecuteTransient(conn, query, &sqlitex.ExecOptions{
		Args: args,
	})
}

// Query executes a SQL query and calls fn for each row
func (db *DB) Query(query string, fn func(*sqlite.Stmt) error, args ...any) error {
	conn, err := db.pool.Take(context.Background())
	if err != nil {
		return fmt.Errorf("failed to get connection from pool: %w", err)
	}
	defer db.pool.Put(conn)

	if len(args) == 0 {
		return sqlitex.ExecuteTransient(conn, query, &sqlitex.ExecOptions{
			ResultFunc: fn,
		})
	}

	return sqlitex.ExecuteTransient(conn, query, &sqlitex.ExecOptions{
		Args:       args,
		ResultFunc: fn,
	})
}

// Begin starts a new transaction
func (db *DB) Begin() (*Tx, error) {
	conn, err := db.pool.Take(context.Background())
	if err != nil {
		return nil, fmt.Errorf("failed to get connection from pool: %w", err)
	}

	if err := sqlitex.ExecuteTransient(conn, "BEGIN", nil); err != nil {
		db.pool.Put(conn)
		return nil, fmt.Errorf("failed to begin transaction: %w", err)
	}

	return &Tx{conn: conn, pool: db.pool}, nil
}

// Transaction runs a function within a transaction
func (db *DB) Transaction(fn func(*Tx) error) error {
	tx, err := db.Begin()
	if err != nil {
		return err
	}

	if err := fn(tx); err != nil {
		tx.Rollback()
		return err
	}

	return tx.Commit()
}

// Tx represents a database transaction
type Tx struct {
	conn *sqlite.Conn
	pool *sqlitex.Pool
}

// Exec executes a SQL statement within the transaction
func (tx *Tx) Exec(query string, args ...any) error {
	if len(args) == 0 {
		return sqlitex.ExecuteTransient(tx.conn, query, nil)
	}

	return sqlitex.ExecuteTransient(tx.conn, query, &sqlitex.ExecOptions{
		Args: args,
	})
}

// Query executes a SQL query within the transaction
func (tx *Tx) Query(query string, fn func(*sqlite.Stmt) error, args ...any) error {
	if len(args) == 0 {
		return sqlitex.ExecuteTransient(tx.conn, query, &sqlitex.ExecOptions{
			ResultFunc: fn,
		})
	}

	return sqlitex.ExecuteTransient(tx.conn, query, &sqlitex.ExecOptions{
		Args:       args,
		ResultFunc: fn,
	})
}

// Commit commits the transaction
func (tx *Tx) Commit() error {
	defer tx.pool.Put(tx.conn)
	return sqlitex.ExecuteTransient(tx.conn, "COMMIT", nil)
}

// Rollback rolls back the transaction
func (tx *Tx) Rollback() error {
	defer tx.pool.Put(tx.conn)
	return sqlitex.ExecuteTransient(tx.conn, "ROLLBACK", nil)
}