package fs

import (
	"io/fs"
	"mime"
	"strings"

	"tildegit.org/tjp/gus"
)

// ResolveFile finds a file from a filesystem based on a request path.
//
// It only returns a non-nil file if a file is found - not a directory.
// If there is any other sort of filesystem access error, it will be
// returned.
func ResolveFile(request *gus.Request, fileSystem fs.FS) (string, fs.File, error) {
	filepath := strings.TrimPrefix(request.Path, "/")
	file, err := fileSystem.Open(filepath)
	if isNotFound(err) {
		return "", nil, nil
	}
	if err != nil {
		return "", nil, err
	}

	isDir, err := fileIsDir(file)
	if err != nil {
		_ = file.Close()
		return "", nil, err
	}

	if isDir {
		_ = file.Close()
		return "", nil, nil
	}

	return filepath, file, nil
}

func mediaType(filePath string) string {
	if strings.HasSuffix(filePath, ".gmi") {
		// This may not be present in the listings searched by mime.TypeByExtension,
		// so provide a dedicated fast path for it here.
		return "text/gemini"
	}

	slashIdx := strings.LastIndex(filePath, "/")
	dotIdx := strings.LastIndex(filePath[slashIdx+1:], ".")
	if dotIdx == -1 {
		return "application/octet-stream"
	}
	ext := filePath[slashIdx+1+dotIdx:]

	mtype := mime.TypeByExtension(ext)
	if mtype == "" {
		return "application/octet-stream"
	}
	return mtype
}