package db

import (
	"database/sql"
	"fmt"
	"os"
	"path/filepath"
	"syscall"

	_ "modernc.org/sqlite"
)

type DBConfig struct {
	JournalMode string
	Synchronous string
	BusyTimeout int
}

func OpenDB(path string, config *DBConfig) (*sql.DB, error) {
	dir := filepath.Dir(path)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return nil, fmt.Errorf("failed to create database directory: %w", err)
	}

	// Check if database file exists and get file info for diagnostics
	var fileInfo os.FileInfo
	if info, err := os.Stat(path); err == nil {
		fileInfo = info
	}

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

	if err := db.Ping(); err != nil {
		db.Close()
		
		// Enhanced error diagnostics
		diag := fmt.Sprintf("database path: %s", path)
		if fileInfo != nil {
			diag += fmt.Sprintf(", file size: %d bytes, mode: %s", fileInfo.Size(), fileInfo.Mode())
		}
		
		// Check directory permissions
		if dirInfo, err := os.Stat(dir); err == nil {
			diag += fmt.Sprintf(", dir mode: %s", dirInfo.Mode())
		}
		
		// Check if it's a file system issue
		if pathErr, ok := err.(*os.PathError); ok {
			if pathErr.Err == syscall.ENOSPC {
				diag += ", filesystem full"
			} else if pathErr.Err == syscall.EACCES {
				diag += ", permission denied"
			}
		}
		
		return nil, fmt.Errorf("failed to ping database: %w (%s)", err, diag)
	}

	// Set default config if not provided
	if config == nil {
		config = &DBConfig{
			JournalMode: "DELETE",
			Synchronous: "FULL",
			BusyTimeout: 10000,
		}
	}

	pragmas := []string{
		fmt.Sprintf("PRAGMA journal_mode=%s", config.JournalMode),
		"PRAGMA foreign_keys=ON",
		fmt.Sprintf("PRAGMA synchronous=%s", config.Synchronous),
		fmt.Sprintf("PRAGMA busy_timeout=%d", config.BusyTimeout),
		"PRAGMA temp_store=MEMORY",
		"PRAGMA mmap_size=268435456",
	}

	for _, pragma := range pragmas {
		if _, err := db.Exec(pragma); err != nil {
			db.Close()
			return nil, fmt.Errorf("failed to set pragma: %w", err)
		}
	}

	return db, nil
}

func EnsureSchema(db *sql.DB) error {
	schema := `
	CREATE TABLE IF NOT EXISTS users (
		id INTEGER PRIMARY KEY AUTOINCREMENT,
		username TEXT NOT NULL UNIQUE,
		token TEXT NOT NULL,
		created_at TEXT NOT NULL,
		updated_at TEXT NOT NULL
	);
	CREATE INDEX IF NOT EXISTS idx_users_token ON users(token);
	`

	if _, err := db.Exec(schema); err != nil {
		return fmt.Errorf("failed to create schema: %w", err)
	}

	return nil
}