package tl

import (
	"html/template"
	"io/fs"
	"os"
	"path"
	"path/filepath"
	"strings"
)

// Template collection.
type Collection struct {
	// Path to the directory with templates.
	RootDir string
	// By default, template name is it's path relative to [RootDir].
	// This prefix will be prepended to a template name: Prefix + "/" + RelativePath.
	// You can leave it empty, then it will be ignored.
	Prefix string
}

// Advanced options.
type Options struct {
	// Files from shared collections will be available in every main template.
	SharedCollections []Collection
}

// Load templates from specified directories with default options.
// Files from the main collection will be added to the returned map.
func Load(mainCollection Collection) (map[string]*template.Template, error) {
	return LoadWithOptions(mainCollection, Options{})
}

// Load templates from specified directories.
// Files from [mainTemplates] collection will be added to the returned map.
func LoadWithOptions(
	mainCollection Collection,
	options Options,
) (map[string]*template.Template, error) {
	sharedTemplate := template.New("")
	for _, stp := range options.SharedCollections {
		files, err := getFiles(stp.RootDir, stp.Prefix)
		if err != nil {
			return nil, err
		}

		for name, contents := range files {
			sharedTemplate, err = sharedTemplate.New(name).Parse(contents)
			if err != nil {
				return nil, err
			}
		}
	}

	templateFiles, err := getFiles(mainCollection.RootDir, mainCollection.Prefix)
	if err != nil {
		return nil, err
	}

	res := make(map[string]*template.Template)
	for name, contents := range templateFiles {
		clone, err := sharedTemplate.Clone()
		if err != nil {
			return nil, err
		}

		res[name], err = clone.New(name).Parse(contents)
		if err != nil {
			return nil, err
		}
	}

	return res, nil
}

func getFiles(root string, keyPrefix string) (map[string]string, error) {
	res := make(map[string]string)
	if !strings.HasSuffix(root, "/") {
		root += "/"
	}

	err := filepath.WalkDir(root, func(entrypath string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}

		if d.IsDir() {
			return nil
		}

		shortPath := path.Join(keyPrefix, strings.TrimPrefix(entrypath, root))
		contents, err := os.ReadFile(entrypath)
		if err != nil {
			return err
		}

		res[shortPath] = string(contents)
		return nil
	})

	return res, err
}