/*
Copyright 2017 The Kubernetes Authors.

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 (
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"text/template"
	"time"

	"gopkg.in/yaml.v2"
)

var (
	sigsYamlFile        = "sigs.yaml"
	templateDir         = "generator"
	sigIndexTemplate    = filepath.Join(templateDir, "sig_index.tmpl")
	wgIndexTemplate     = filepath.Join(templateDir, "wg_index.tmpl")
	listTemplate        = filepath.Join(templateDir, "sig_list.tmpl")
	headerTemplate      = filepath.Join(templateDir, "header.tmpl")
	sigListOutput       = "sig-list.md"
	sigIndexOutput      = "README.md"
	githubTeamNames     = []string{"misc", "test-failures", "bugs", "feature-requests", "proposals", "pr-reviews", "api-reviews"}
	beginMarker         = "<!-- BEGIN CUSTOM CONTENT -->"
	endMarker           = "<!-- END CUSTOM CONTENT -->"
	lastGeneratedPrefix = "Last generated: "
)

type Lead struct {
	Name    string
	Company string
	GitHub  string
}

type Meeting struct {
	Day       string
	UTC       string
	PST       string
	Frequency string
}

type Contact struct {
	Slack            string
	MailingList      string `yaml:"mailing_list"`
	FullGitHubTeams  bool   `yaml:"full_github_teams"`
	GithubTeamPrefix string `yaml:"github_team_prefix"`
	GithubTeamNames  []string
}

type Sig struct {
	Name              string
	Dir               string
	MissionStatement  string `yaml:"mission_statement"`
	Leads             []Lead
	Meetings          []Meeting
	MeetingURL        string `yaml:"meeting_url"`
	MeetingArchiveURL string `yaml:"meeting_archive_url"`
	Contact           Contact
}

type Wg struct {
	Name              string
	Dir               string
	MissionStatement  string `yaml:"mission_statement"`
	Organizers        []Lead
	Meetings          []Meeting
	MeetingURL        string `yaml:"meeting_url"`
	MeetingArchiveURL string `yaml:"meeting_archive_url"`
	Contact           Contact
}

type Context struct {
	Sigs          []Sig
	WorkingGroups []Wg
}

type SigEntries struct {
	Sigs []Sig
}

func (slice SigEntries) Len() int {
	return len(slice.Sigs)
}

func (slice SigEntries) Less(i, j int) bool {
	return slice.Sigs[i].Name < slice.Sigs[j].Name
}

func (slice SigEntries) Swap(i, j int) {
	slice.Sigs[i], slice.Sigs[j] = slice.Sigs[j], slice.Sigs[i]
}

type WgEntries struct {
	WorkingGroups []Wg
}

func (slice WgEntries) Len() int {
	return len(slice.WorkingGroups)
}

func (slice WgEntries) Less(i, j int) bool {
	return slice.WorkingGroups[i].Name < slice.WorkingGroups[j].Name
}

func (slice WgEntries) Swap(i, j int) {
	slice.WorkingGroups[i], slice.WorkingGroups[j] = slice.WorkingGroups[j], slice.WorkingGroups[i]
}

func pathExists(path string) bool {
	_, err := os.Stat(path)
	return err == nil
}

func createDirIfNotExists(path string) error {
	if !pathExists(path) {
		fmt.Printf("%s directory does not exist, creating\n", path)
		return os.Mkdir(path, 0755)
	}
	return nil
}

func getExistingContent(path string) (string, error) {
	capture := false
	var captured []string

	// NOTE: For some reason using bufio.Scanner with existing file pointer prepends
	// a bunch of null ^@ characters, so using to ioutil.ReadFile instead.
	content, err := ioutil.ReadFile(path)
	if err != nil {
		return "", err
	}

	for _, line := range strings.Split(string(content), "\n") {
		if strings.Contains(line, endMarker) {
			capture = false
		}
		if capture {
			captured = append(captured, line)
		}
		if strings.Contains(line, beginMarker) {
			capture = true
		}
	}

	return strings.Join(captured, "\n"), nil
}

func writeTemplate(templatePath, outputPath string, data interface{}) error {
	// set up template
	t, err := template.ParseFiles(templatePath, headerTemplate)
	if err != nil {
		return err
	}

	// create if not exists
	if !pathExists(outputPath) {
		_, err := os.Create(outputPath)
		if err != nil {
			return err
		}
	}

	// open file and truncate
	f, err := os.OpenFile(outputPath, os.O_RDWR, 0644)
	if err != nil {
		return err
	}
	defer f.Close()

	// get any existing content
	content, err := getExistingContent(outputPath)
	if err != nil {
		return err
	}

	// ensure file is empty
	f.Truncate(0)

	// generated content
	err = t.Execute(f, data)
	if err != nil {
		return err
	}

	// custom content block
	writeCustomContentBlock(f, content)

	// last generated
	writeLastGenerated(f)

	fmt.Printf("Generated %s\n", outputPath)
	return nil
}

func writeCustomContentBlock(f *os.File, content string) {
	lines := []string{beginMarker, "\n", content, "\n", endMarker, "\n"}
	for _, line := range lines {
		f.Write([]byte(line))
	}
}

func writeLastGenerated(f *os.File) {
	lastGenerated := fmt.Sprintf("\n%s %s", lastGeneratedPrefix, time.Now().Format("Mon Jan 2 2006 15:04:05"))
	f.Write([]byte(lastGenerated))
}

func createReadmeFiles(ctx Context) error {
	var selectedSig *string
	if sig, ok := os.LookupEnv("SIG"); ok {
		selectedSig = &sig
	}
	for _, sig := range ctx.Sigs {
		dirName := fmt.Sprintf("sig-%s", strings.ToLower(strings.Replace(sig.Name, " ", "-", -1)))

		if selectedSig != nil && *selectedSig != dirName {
			fmt.Printf("Skipping %s\n", dirName)
			continue
		}

		createDirIfNotExists(dirName)

		prefix := sig.Contact.GithubTeamPrefix
		if prefix == "" {
			prefix = dirName
		}

		for _, gtn := range githubTeamNames {
			sig.Contact.GithubTeamNames = append(sig.Contact.GithubTeamNames, fmt.Sprintf("%s-%s", prefix, gtn))
		}

		outputPath := fmt.Sprintf("%s/%s", dirName, sigIndexOutput)
		if err := writeTemplate(sigIndexTemplate, outputPath, sig); err != nil {
			return err
		}
	}
	var selectedWg *string
	if wg, ok := os.LookupEnv("WG"); ok {
		selectedWg = &wg
	}
	for _, wg := range ctx.WorkingGroups {
		dirName := fmt.Sprintf("wg-%s", strings.ToLower(strings.Replace(wg.Name, " ", "-", -1)))

		if selectedWg != nil && *selectedWg != dirName {
			fmt.Printf("Skipping %s\n", dirName)
			continue
		}

		createDirIfNotExists(dirName)

		prefix := wg.Contact.GithubTeamPrefix
		if prefix == "" {
			prefix = dirName
		}

		for _, gtn := range githubTeamNames {
			wg.Contact.GithubTeamNames = append(wg.Contact.GithubTeamNames, fmt.Sprintf("%s-%s", prefix, gtn))
		}

		outputPath := fmt.Sprintf("%s/%s", dirName, sigIndexOutput)
		if err := writeTemplate(wgIndexTemplate, outputPath, wg); err != nil {
			return err
		}
	}

	return nil
}

func createListFile(ctx Context) error {
	return writeTemplate(listTemplate, sigListOutput, ctx)
}

func main() {
	yamlData, err := ioutil.ReadFile(sigsYamlFile)
	if err != nil {
		log.Fatal(err)
	}

	var ctx Context
	err = yaml.Unmarshal(yamlData, &ctx)
	if err != nil {
		log.Fatal(err)
	}
	sigEntries := SigEntries{ctx.Sigs}
	sort.Sort(sigEntries)
	ctx.Sigs = sigEntries.Sigs
	wgEntries := WgEntries{ctx.WorkingGroups}
	sort.Sort(wgEntries)
	ctx.WorkingGroups = wgEntries.WorkingGroups

	err = createReadmeFiles(ctx)
	if err != nil {
		log.Fatal(err)
	}

	err = createListFile(ctx)
	if err != nil {
		log.Fatal(err)
	}

	fmt.Println("Finished generation!")
}