package main

import (
	"fmt"
	"io/ioutil"
	"os"
	"sort"
	"strings"
	"time"

	"github.com/gocolly/colly"
	log "github.com/sirupsen/logrus"
)

type wikiPage struct {
	name string
	url  string
}

func main() {
	log.Infof("Tildes Wiki Sitemap\n")
	// Create a variable we'll use to check if a current sitemap already exists
	_, sitemapExists := os.Stat("sitemap.md")
	if sitemapExists == nil {
		// If it does exist, rename it to "previous"
		os.Rename("sitemap.md", "previous-sitemap.md")
	}

	// Create a groups array, which will be used to sort the output
	// (couldn't figure out how to sort a map by keys)
	groups := make([]string, 0)
	// Create a map for the pages where the key will be the group name
	pages := make(map[string][]wikiPage)

	// Create a new collector that's only allowed to visit Tildes.net
	collector := colly.NewCollector(colly.AllowedDomains("tildes.net"))

	// When receiving HTML:
	collector.OnHTML("html", func(page *colly.HTMLElement) {
		time.Sleep(time.Second)
		// Define the URL for brevity
		url := page.Request.URL.String()
		if strings.HasSuffix(url, "/groups") {
			// If the URL ends with /groups we want to visit each group found in the table
			page.ForEach("td>.link-group", func(_ int, element *colly.HTMLElement) {
				log.Printf("Visiting group %s", element.Text)
				groups = append(groups, element.Text)
				// Make the pages for all groups start out as an empty array
				// This makes it so groups without any wiki pages also get added to the output, instead of being skipped
				pages[element.Text] = make([]wikiPage, 0)
				collector.Visit(fmt.Sprintf("https://tildes.net/%s", element.Text))
			})
		} else if strings.Contains(url, "~") {
			// Else if the URL has a tilde in it, we want to extract the wiki pages
			group := url[strings.LastIndex(url, "/")+1:]
			page.ForEach(".nav>.nav-item>a", func(_ int, element *colly.HTMLElement) {
				// Append the new page to the array and set its name and URL
				pages[group] = append(pages[group], wikiPage{
					name: element.Text,
					url:  element.Attr("href"),
				})
				log.Printf("Found wiki page: %s/%s", group, element.Text)
			})
		}
	})

	// After defining the OnHTML callback, visit the group listing
	// This won't finish until all groups have been visited inside and the entire callback is done
	collector.Visit("https://tildes.net/groups")

	// Create the sitemap.md file
	file, _ := os.Create("sitemap.md")
	defer file.Close()
	// Write the boilerplate stuff first
	file.WriteString("# Tildes Wiki Sitemap\n\n")
	file.WriteString("Automatically generated by [this program](https://gitlab.com/bauke/tildes-wiki-sitemap). [PM @Bauke](https://tildes.net/user/Bauke/new_message) if this page is outdated and you can't run the program yourself.\n\n")
	file.WriteString("This page is a temporary placeholder to help wiki contributors navigate. Find this page easily by bookmarking it!\n\n")
	// Sort the groups
	sort.Strings(groups)
	// Define a variable that will keep track of the pages count
	pagesTotal := 0
	// Write a . to indicate the start of the tree
	file.WriteString(".\n")
	// Iterate over the group names
	for index, group := range groups {
		prefix := ""
		if index == len(groups)-1 {
			// If we're at the last group, write the "L" piece instead
			file.WriteString(fmt.Sprintf("└── [%s](https://tildes.net/%s/wiki)\n", group[1:], group))
			// And because there doesn't have to be an extra vertical piece here, we need to preserve the leading space
			// So we set the prefix to 2 non-breaking spaces, Markdown won't remove these
			prefix = "  "
		} else {
			// Else we're not at the last group yet, so we wanna use the rotated "T" piece
			file.WriteString(fmt.Sprintf("├── [%s](https://tildes.net/%s/wiki)\n", group[1:], group))
			prefix = "│ "
		}
		for pageIndex, page := range pages[group] {
			// Increment the total pages
			pagesTotal++
			// Write the prefix determined earlier
			file.WriteString(prefix)
			if pageIndex == len(pages[group])-1 {
				// Same reasoning as with the groups, if we're on the last page use the "L" piece
				file.WriteString("└")
			} else {
				// Otherwise the rotated "T"
				file.WriteString("├")
			}
			// And then write the Markdown link
			file.WriteString(fmt.Sprintf("── [%s](%s)\n", page.name, page.url))
		}
	}

	// And finally write how many groups and pages there are, like `tree` writes directories and files
	file.WriteString(fmt.Sprintf("\n%v groups, %v pages\n", len(groups), pagesTotal))

	// If the sitemap exists we want to read both sitemaps and check if they're the same
	if sitemapExists == nil {
		file, err := os.Open("sitemap.md")
		if err != nil {
			log.Fatal(err)
		}

		current, _ := ioutil.ReadAll(file)
		file.Close()
		file, err = os.Open("previous-sitemap.md")
		if err != nil {
			log.Fatal(err)
		}

		previous, _ := ioutil.ReadAll(file)
		file.Close()

		// If they're the same just log that all is good, if not warn that we need to update
		if string(current) == string(previous) {
			log.Infof("Current and previous sitemaps are the same, no need to update.\n")
		} else {
			log.Warnf("Current and previous sitemaps are not the same, you should update it.\n")
		}
	}

	log.Printf("Done! Found %v groups and %v pages, see sitemap.md for the output", len(groups), pagesTotal)
}