// Package templates embeds the shipped typst templates so the mopac-pdf
// binary is self-contained: the engine container only ever sees the
// prepared compile root.
package templates

import (
	"embed"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

//go:embed *.typ
var embedded embed.FS

// Names lists the shipped template names ("report", "brief").
func Names() []string {
	entries, err := embedded.ReadDir(".")
	if err != nil {
		return nil
	}
	var names []string
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".typ") {
			names = append(names, strings.TrimSuffix(e.Name(), ".typ"))
		}
	}
	return names
}

// Source returns the template source for name: from dir when set (custom
// template drop-in), else the embedded copy.
func Source(dir, name string) (string, error) {
	if strings.ContainsAny(name, `/\.`) || name == "" {
		return "", fmt.Errorf("template: invalid name %q", name)
	}
	if dir != "" {
		data, err := os.ReadFile(filepath.Join(dir, name+".typ"))
		if err == nil {
			return string(data), nil
		}
		if !os.IsNotExist(err) {
			return "", err
		}
	}
	data, err := embedded.ReadFile(name + ".typ")
	if err != nil {
		return "", fmt.Errorf("template %q not found (shipped: %s)", name, strings.Join(Names(), ", "))
	}
	return string(data), nil
}