// Copyright 2023 wanderer <a_mirre at utb dot cz>
// SPDX-License-Identifier: AGPL-3.0-only

package template

import (
	"html/template"
	"io/fs"
	"os"
	"strings"

	"git.dotya.ml/mirre-mt/pcmt/app/settings"
	"git.dotya.ml/mirre-mt/pcmt/modules/funcmap"
	"git.dotya.ml/mirre-mt/pcmt/slogging"
	"golang.org/x/exp/slog"
)

type tplMap map[string]*template.Template

var (
	templateMap tplMap
	// embedded templates.
	tmplFS  fs.FS
	setting *settings.Settings
	// global logger.
	slogger *slogging.Slogger
	// local logger copy.
	log slogging.Slogger
	// path to "templates" folder (empty if LiveMode).
	tmplPath   string
	tmplSuffix = ".tmpl"
)

// Init saves settings and embedded templates to package-level state and also
// "initialises" template rendering.
func Init(s *settings.Settings, tmpls fs.FS) {
	slogger = slogging.Logger()
	log = *slogger // have a local copy.
	log.Logger = log.Logger.With(
		slog.Group("pcmt extra", slog.String("module", "modules/template")),
	)

	setting = s

	tmplPath = setting.TemplatesPath() // will be empty if LiveMode.

	initTemplates(tmpls)

	log.Debug(Renderer.tmpls.DefinedTemplates())
}

// Get returns a template requested either from the tmplPath (in LiveMode) or
// from the pre-compiled tmpl list set directly to Renderer.
func Get(name string) *template.Template {
	liveMode := setting.IsLive()

	if liveMode {
		log.Debug("re-reading tmpls") // TODO: only re-read the tmpl in question.

		allTmpls := listAll(tmplSuffix)

		// create fresh tmpl root.
		t := template.New("")

		for i, v := range allTmpls {
			rawfile, err := os.ReadFile(v)
			if err != nil {
				panic(err)
			}

			allTmpls[i] = strings.TrimPrefix(v, tmplPath+"/")

			t = t.New(allTmpls[i]).Funcs(funcmap.FuncMap())

			template.Must(t.Parse(string(rawfile)))
		}

		Renderer.tmpls = t
	}

	return Renderer.tmpls.Lookup(name)
}

func initTemplates(f fs.FS) {
	if !setting.IsLive() {
		if f != nil || f != tmplFS {
			tmplFS = f
		}
	}

	allTmpls := listAll(tmplSuffix)
	t := Renderer.tmpls

	// ensure this fails at compile time, if at all ("Must").
	if !setting.IsLive() {
		for i, v := range allTmpls {
			rawfile, err := fs.ReadFile(tmplFS, v)
			if err != nil {
				panic(err)
			}

			allTmpls[i] = strings.TrimPrefix(v, "templates/")

			t := Renderer.tmpls.New(allTmpls[i]).Funcs(funcmap.FuncMap())
			template.Must(t.Parse(string(rawfile)))
		}

		Renderer.tmpls = t
	} else {
		for i, v := range allTmpls {
			rawfile, err := os.ReadFile(v)
			if err != nil {
				panic(err)
			}

			allTmpls[i] = strings.TrimPrefix(v, tmplPath+"/")
			t = Renderer.tmpls.New(allTmpls[i]).Funcs(funcmap.FuncMap())

			template.Must(t.Parse(string(rawfile)))
		}

		Renderer.tmpls = t
	}

	makeTplMap(Renderer.tmpls, allTmpls)
}

func makeTplMap(tpl *template.Template, tplList []string) {
	allTmpls := tplList

	var tp tplMap

	if templateMap == nil {
		tp = make(tplMap, len(allTmpls))
	} else {
		tp = templateMap
	}

	for _, v := range allTmpls {
		tp[v] = tpl.Lookup(v)
	}

	templateMap = tp
}