package common

import (
	"fmt"
	"path/filepath"
	"strings"

	"dawn.googlesource.com/dawn/tools/src/fileutils"
	"dawn.googlesource.com/dawn/tools/src/oswrapper"
)

// StaleFiles is a list of generated file paths that need updating
type StaleFiles []string

func (l StaleFiles) Error() string {
	// TODO(crbug.com/344014313): Update StaleFiles to be more than a type alias
	// so it can hold a reference to a FilesystemReader for dependency injection.
	projectRoot := fileutils.DawnRoot(oswrapper.GetRealOSWrapper())
	msg := &strings.Builder{}
	fmt.Fprintln(msg, len(l), "files need regenerating:")
	for _, path := range l {
		if rel, err := filepath.Rel(projectRoot, path); err == nil {
			fmt.Fprintln(msg, " •", rel)
		} else {
			fmt.Fprintln(msg, " •", path)
		}
	}
	fmt.Fprintln(msg, "Regenerate these files with: ./tools/run gen")
	return msg.String()
}