/*
Copyright 2017-2022 CAcert Inc.
SPDX-License-Identifier: Apache-2.0

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package main

import (
	"bytes"
	"crypto/x509"
	"encoding/pem"
	"errors"
	"fmt"
	"html/template"
	"io/fs"
	"net/http"
	"path/filepath"
	"runtime/debug"
	"strconv"
	"strings"

	"github.com/Masterminds/sprig/v3"
	"github.com/go-playground/form/v4"
	"github.com/julienschmidt/httprouter"
	"github.com/justinas/nosurf"

	"git.cacert.org/cacert-boardvoting/internal/models"
	"git.cacert.org/cacert-boardvoting/ui"
)

func (app *application) serverError(w http.ResponseWriter, err error) {
	trace := fmt.Sprintf("%s\n%s", err.Error(), debug.Stack())

	_ = app.errorLog.Output(2, trace)

	http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
}

func (app *application) clientError(w http.ResponseWriter, status int) {
	http.Error(w, http.StatusText(status), status)
}

func (app *application) notFound(w http.ResponseWriter) {
	app.clientError(w, http.StatusNotFound)
}

func (app *application) decodePostForm(r *http.Request, dst any) error {
	err := r.ParseForm()
	if err != nil {
		return fmt.Errorf("could not parse HTML form: %w", err)
	}

	err = app.formDecoder.Decode(dst, r.PostForm)
	if err != nil {
		var invalidDecoderError *form.InvalidDecoderError

		if errors.As(err, &invalidDecoderError) {
			panic(err)
		}

		return fmt.Errorf("could not decode form: %w", err)
	}

	return nil
}

func newTemplateCache() (map[string]*template.Template, error) {
	cache := map[string]*template.Template{}

	pages, err := fs.Glob(ui.Files, "html/pages/*.html")
	if err != nil {
		return nil, fmt.Errorf("could not find page templates: %w", err)
	}

	funcMaps := sprig.FuncMap()
	funcMaps["nl2br"] = func(text string) template.HTML {
		// #nosec G203 input is sanitized
		return template.HTML(strings.ReplaceAll(template.HTMLEscapeString(text), "\n", "<br>"))
	}
	funcMaps["canManageUsers"] = func(v *models.User) (bool, error) {
		return checkRole(v, models.RoleSecretary, models.RoleAdmin)
	}
	funcMaps["canVote"] = func(v *models.User) (bool, error) {
		return checkRole(v, models.RoleVoter)
	}
	funcMaps["canStartVote"] = func(v *models.User) (bool, error) {
		return checkRole(v, models.RoleVoter)
	}

	for _, page := range pages {
		name := filepath.Base(page)

		ts, err := template.New("").Funcs(funcMaps).ParseFS(
			ui.Files,
			"html/base.html",
			"html/partials/*.html",
			page,
		)
		if err != nil {
			return nil, fmt.Errorf("could not parse base template: %w", err)
		}

		cache[name] = ts
	}

	return cache, nil
}

type templateData struct {
	PrevPage     string
	NextPage     string
	Motion       *models.Motion
	Motions      []*models.Motion
	User         *models.User
	Users        []*models.User
	Request      *http.Request
	Flashes      []FlashMessage
	Form         any
	ActiveNav    topLevelNavItem
	ActiveSubNav subLevelNavItem
	CSRFToken    string
}

func (app *application) newTemplateData(
	r *http.Request,
	nav topLevelNavItem,
	subNav subLevelNavItem,
) *templateData {
	user, _ := app.GetUser(r)

	return &templateData{
		Request:      r,
		User:         user,
		ActiveNav:    nav,
		ActiveSubNav: subNav,
		Flashes:      app.flashes(r),
		CSRFToken:    nosurf.Token(r),
	}
}

func (app *application) render(w http.ResponseWriter, status int, page string, data *templateData) {
	ts, ok := app.templateCache[page]
	if !ok {
		app.serverError(w, fmt.Errorf("the template %s does not exist", page))

		return
	}

	buf := new(bytes.Buffer)

	err := ts.ExecuteTemplate(buf, "base", data)
	if err != nil {
		app.serverError(w, err)

		return
	}

	w.WriteHeader(status)

	_, _ = buf.WriteTo(w)
}

func (app *application) motionFromRequestParam(
	w http.ResponseWriter,
	r *http.Request,
	params httprouter.Params,
) *models.Motion {
	tag := params.ByName("tag")

	withVotes := r.URL.Query().Has("showvotes")

	motion, err := app.motions.ByTag(r.Context(), tag, withVotes)
	if err != nil {
		app.serverError(w, err)

		return nil
	}

	if motion.ID == 0 {
		app.notFound(w)

		return nil
	}

	return motion
}

func (app *application) userFromRequestParam(
	w http.ResponseWriter, r *http.Request, params httprouter.Params, options ...models.UserListOption,
) *models.User {
	userID, err := strconv.Atoi(params.ByName("id"))
	if err != nil {
		app.clientError(w, http.StatusBadRequest)

		return nil
	}

	user, err := app.users.ByID(r.Context(), int64(userID), options...)
	if err != nil {
		app.serverError(w, err)

		return nil
	}

	if user == nil {
		app.notFound(w)

		return nil
	}

	return user
}

func (app *application) choiceFromRequestParam(w http.ResponseWriter, params httprouter.Params) *models.VoteChoice {
	choiceParam := params.ByName("choice")

	choice, err := models.VoteChoiceFromString(choiceParam)
	if err != nil {
		app.clientError(w, http.StatusBadRequest)

		return nil
	}

	return choice
}

func getPEMClientCert(r *http.Request) (string, error) {
	cert := r.Context().Value(ctxAuthenticatedCert)

	authenticatedCertificate, ok := cert.(*x509.Certificate)
	if !ok {
		return "", errors.New("could not handle certificate as x509.Certificate")
	}

	clientCertPEM := bytes.NewBuffer(make([]byte, 0))

	err := pem.Encode(clientCertPEM, &pem.Block{Type: "CERTIFICATE", Bytes: authenticatedCertificate.Raw})
	if err != nil {
		return "", fmt.Errorf("error encoding client certificate: %w", err)
	}

	return clientCertPEM.String(), nil
}

type FlashVariant string

const (
	flashWarning FlashVariant = "warning"
	flashInfo    FlashVariant = "info"
	flashSuccess FlashVariant = "success"
	flashError   FlashVariant = "error"
)

type FlashMessage struct {
	Variant FlashVariant
	Title   string
	Message string
}

func (app *application) addFlash(r *http.Request, message *FlashMessage) {
	flashes := app.flashes(r)

	flashes = append(flashes, *message)

	app.sessionManager.Put(
		r.Context(),
		"flashes",
		flashes,
	)
}

func (app *application) flashes(r *http.Request) []FlashMessage {
	flashInstance := app.sessionManager.Pop(r.Context(), "flashes")

	if flashInstance != nil {
		flashes, ok := flashInstance.([]FlashMessage)

		if ok {
			return flashes
		}
	}

	return make([]FlashMessage, 0)
}