/*
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"
	"fmt"
	"html/template"
	"io/fs"
	"net/http"
	"path/filepath"
	"strings"
	"time"

	"github.com/Masterminds/sprig/v3"
	"github.com/gorilla/csrf"

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

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(*models.Voter) bool {
		return false
	}
	funcMaps[csrf.TemplateTag] = csrf.TemplateField

	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 {
	Voter   *models.Voter
	Flashes []string
	Params  struct {
		Flags struct {
			Unvoted bool
		}
	}
	PrevPage, NextPage string
	Motions            []*models.MotionForDisplay
}

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 (m *templateData) setPaginationParameters(first, last *time.Time) error {
	motions := m.Motions

	if len(motions) > 0 && first.Before(motions[len(motions)-1].Proposed) {
		marshalled, err := motions[len(motions)-1].Proposed.MarshalText()
		if err != nil {
			return fmt.Errorf("could not serialize timestamp: %w", err)
		}

		m.NextPage = string(marshalled)
	}

	if len(motions) > 0 && last.After(motions[0].Proposed) {
		marshalled, err := motions[0].Proposed.MarshalText()
		if err != nil {
			return fmt.Errorf("could not serialize timestamp: %w", err)
		}

		m.PrevPage = string(marshalled)
	}

	return nil
}

func (app *application) motionList(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/motions/" {
		app.notFound(w)

		return
	}

	var (
		listOptions *models.MotionListOptions
		err         error
	)

	listOptions, err = calculateMotionListOptions(r)
	if err != nil {
		app.clientError(w, http.StatusBadRequest)

		return
	}

	ctx := r.Context()

	motions, err := app.motions.GetMotions(ctx, listOptions)
	if err != nil {
		app.serverError(w, err)

		return
	}

	first, last, err := app.motions.TimestampRange(ctx)
	if err != nil {
		app.serverError(w, err)

		return
	}

	templateData := &templateData{Motions: motions}

	err = templateData.setPaginationParameters(first, last)
	if err != nil {
		app.serverError(w, err)

		return
	}

	app.render(w, http.StatusOK, "motions.html", templateData)
}

func calculateMotionListOptions(r *http.Request) (*models.MotionListOptions, error) {
	const (
		queryParamBefore = "before"
		queryParamAfter  = "after"
		motionsPerPage   = 10
	)

	listOptions := &models.MotionListOptions{Limit: motionsPerPage}

	if r.URL.Query().Has(queryParamAfter) {
		var after time.Time

		err := after.UnmarshalText([]byte(r.URL.Query().Get(queryParamAfter)))
		if err != nil {
			return nil, fmt.Errorf("could not unmarshal timestamp: %w", err)
		}

		listOptions.After = &after
	} else if r.URL.Query().Has(queryParamBefore) {
		var before time.Time

		err := before.UnmarshalText([]byte(r.URL.Query().Get(queryParamBefore)))
		if err != nil {
			return nil, fmt.Errorf("could not unmarshal timestamp: %w", err)
		}

		listOptions.Before = &before
	}

	return listOptions, nil
}

func (app *application) home(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)

		return
	}

	if r.Method != "GET" && r.Method != "HEAD" {
		w.Header().Set("Allow", "GET,HEAD")
		app.clientError(w, http.StatusMethodNotAllowed)

		return
	}

	http.Redirect(w, r, "/motions/", http.StatusMovedPermanently)
}