package main

import (
	"fmt"
	"hash/fnv"
	"io"
	"io/fs"
	"log"
	"log/slog"
	"os"
	"path/filepath"
	"strings"

	"github.com/pkg/errors"
)

type File struct {
	filename string
	etag     string
}

var files = map[string]File{}

func hashFile(filename string) (string, error) {
	f, err := os.Open(filename)
	if err != nil {
		return "", err
	}
	defer f.Close()
	hash := fnv.New64a()
	if _, err := io.Copy(hash, f); err != nil {
		return "", err
	}
	return fmt.Sprintf(`W/"%x"`, hash.Sum(nil)), nil
}

func registerFile(urlpath string, filepath string) error {
	if files[urlpath] != (File{}) {
		log.Printf("registerFile called with duplicate file, urlPath: %s", urlpath)
		return nil
	}
	hash, err := hashFile(filepath)
	if err != nil {
		return err
	}
	files[urlpath] = File{
		filename: filepath,
		etag:     hash,
	}
	return nil
}

func registerContentFiles(root string) error {
	err := filepath.WalkDir(root, func(filePath string, f fs.DirEntry, err error) error {
		if err != nil {
			return errors.WithMessagef(err, "failed to access path %s", filePath)
		}
		relPath, err := filepath.Rel(root, filePath)
		if err != nil {
			return errors.WithMessagef(err, "failed to make path relative, path: %s", filePath)
		}
		urlPath, _ := strings.CutSuffix(relPath, "index.html")
		if !f.IsDir() {
			slog.Debug("registering file", "urlpath", "/"+urlPath)
			return registerFile("/"+urlPath, filePath)
		}
		return nil
	})
	if err != nil {
		return err
	}
	return nil
}

func GetFile(urlPath string) File {
	return files[urlPath]
}