package routers

import (
	"errors"
	"os"
	"path/filepath"
	"strings"
	"sync"
)

// StaticRouter is a filesystem-based router for static files
type StaticRouter struct {
	rootDir string            // Root directory containing files
	routes  map[string]string // Direct mapping from URL path to file path
	mu      sync.RWMutex      // Lock for concurrent access to routes
}

// NewStaticRouter creates a new StaticRouter instance
func NewStaticRouter(rootDir string) (*StaticRouter, error) {
	// Verify root directory exists
	info, err := os.Stat(rootDir)
	if err != nil {
		return nil, err
	}
	if !info.IsDir() {
		return nil, errors.New("root path is not a directory")
	}

	r := &StaticRouter{
		rootDir: rootDir,
		routes:  make(map[string]string),
	}

	// Build routes
	if err := r.buildRoutes(); err != nil {
		return nil, err
	}

	return r, nil
}

// buildRoutes scans the root directory and builds the routing map
func (r *StaticRouter) buildRoutes() error {
	return filepath.Walk(r.rootDir, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}

		// Skip directories
		if info.IsDir() {
			return nil
		}

		// Get relative path for URL
		relPath, err := filepath.Rel(r.rootDir, path)
		if err != nil {
			return err
		}

		// Convert to URL path with forward slashes for consistency
		urlPath := "/" + strings.ReplaceAll(relPath, "\\", "/")

		// Add to routes map
		r.routes[urlPath] = path
		return nil
	})
}

// Match finds a file path for the given URL path
func (r *StaticRouter) Match(path string) (string, bool) {
	r.mu.RLock()
	defer r.mu.RUnlock()

	filePath, found := r.routes[path]
	return filePath, found
}

// Refresh rebuilds the router by rescanning the root directory
func (r *StaticRouter) Refresh() error {
	r.mu.Lock()
	defer r.mu.Unlock()

	// Clear routes
	r.routes = make(map[string]string)

	// Rebuild routes
	return r.buildRoutes()
}