package database

import (
	"fmt"
	"os"
	"path/filepath"
	"runtime"
)

// ResolveDatabasePath determines the appropriate database file location
// based on configuration, system type, and available permissions
func ResolveDatabasePath(configPath string) (string, error) {
	// Use explicit configuration path if provided
	if configPath != "" {
		if err := ensureDirExists(filepath.Dir(configPath)); err != nil {
			return "", fmt.Errorf("cannot create directory for configured path %s: %v", configPath, err)
		}
		return configPath, nil
	}
	
	// Try system location first (for services)
	if systemPath, err := trySystemPath(); err == nil {
		return systemPath, nil
	}
	
	// Try user data directory
	if userPath, err := tryUserPath(); err == nil {
		return userPath, nil
	}
	
	// Fallback to current directory
	return tryCurrentDirPath()
}

// trySystemPath attempts to use system-wide database location
func trySystemPath() (string, error) {
	var systemDir string
	
	switch runtime.GOOS {
	case "linux":
		systemDir = "/var/lib/skyview"
	case "darwin":
		systemDir = "/usr/local/var/skyview"
	case "windows":
		systemDir = filepath.Join(os.Getenv("PROGRAMDATA"), "skyview")
	default:
		return "", fmt.Errorf("system path not supported on %s", runtime.GOOS)
	}
	
	// Check if directory exists and is writable
	if err := ensureDirExists(systemDir); err != nil {
		return "", err
	}
	
	dbPath := filepath.Join(systemDir, "skyview.db")
	
	// Test write permissions
	if err := testWritePermissions(dbPath); err != nil {
		return "", err
	}
	
	return dbPath, nil
}

// tryUserPath attempts to use user data directory
func tryUserPath() (string, error) {
	var userDataDir string
	
	switch runtime.GOOS {
	case "linux":
		if xdgData := os.Getenv("XDG_DATA_HOME"); xdgData != "" {
			userDataDir = xdgData
		} else {
			home, err := os.UserHomeDir()
			if err != nil {
				return "", err
			}
			userDataDir = filepath.Join(home, ".local", "share")
		}
	case "darwin":
		home, err := os.UserHomeDir()
		if err != nil {
			return "", err
		}
		userDataDir = filepath.Join(home, "Library", "Application Support")
	case "windows":
		userDataDir = os.Getenv("APPDATA")
		if userDataDir == "" {
			return "", fmt.Errorf("APPDATA environment variable not set")
		}
	default:
		return "", fmt.Errorf("user path not supported on %s", runtime.GOOS)
	}
	
	skyviewDir := filepath.Join(userDataDir, "skyview")
	
	if err := ensureDirExists(skyviewDir); err != nil {
		return "", err
	}
	
	dbPath := filepath.Join(skyviewDir, "skyview.db")
	
	// Test write permissions
	if err := testWritePermissions(dbPath); err != nil {
		return "", err
	}
	
	return dbPath, nil
}

// tryCurrentDirPath uses current directory as fallback
func tryCurrentDirPath() (string, error) {
	currentDir, err := os.Getwd()
	if err != nil {
		return "", fmt.Errorf("cannot get current directory: %v", err)
	}
	
	dbPath := filepath.Join(currentDir, "skyview.db")
	
	// Test write permissions
	if err := testWritePermissions(dbPath); err != nil {
		return "", err
	}
	
	return dbPath, nil
}

// ensureDirExists creates directory if it doesn't exist
func ensureDirExists(dir string) error {
	if _, err := os.Stat(dir); os.IsNotExist(err) {
		if err := os.MkdirAll(dir, 0755); err != nil {
			return fmt.Errorf("cannot create directory %s: %v", dir, err)
		}
	} else if err != nil {
		return fmt.Errorf("cannot access directory %s: %v", dir, err)
	}
	
	return nil
}

// testWritePermissions verifies write access to the database path
func testWritePermissions(dbPath string) error {
	dir := filepath.Dir(dbPath)
	
	// Check directory write permissions
	testFile := filepath.Join(dir, ".skyview_write_test")
	if err := os.WriteFile(testFile, []byte("test"), 0644); err != nil {
		return fmt.Errorf("no write permission to directory %s: %v", dir, err)
	}
	
	// Clean up test file
	os.Remove(testFile)
	
	return nil
}

// GetDatabaseDirectory returns the directory containing the database file
func GetDatabaseDirectory(dbPath string) string {
	return filepath.Dir(dbPath)
}

// IsSystemPath returns true if the database path is in a system location
func IsSystemPath(dbPath string) bool {
	switch runtime.GOOS {
	case "linux":
		return filepath.HasPrefix(dbPath, "/var/lib/skyview")
	case "darwin":
		return filepath.HasPrefix(dbPath, "/usr/local/var/skyview")
	case "windows":
		programData := os.Getenv("PROGRAMDATA")
		return programData != "" && filepath.HasPrefix(dbPath, filepath.Join(programData, "skyview"))
	}
	return false
}