package main

import (
	"fmt"
	"net/http"
	"strings"
	"time"
)

var outputMode string

type channel struct {
	Title       string
	Link        string
	Name        string
	Description string
	Items       []*post
}

func (c *channel) String() string {
	var template string
	switch outputMode {
	case "html":
		template = htmlRoot
	case "rss":
		template = rssRoot
	}

	var s string
	s = strings.Replace(template, "{{title}}", c.Title, -1)
	s = strings.Replace(s, "{{link}}", c.Link, -1)
	s = strings.Replace(s, "{{description}}", c.Description, -1)
	s = strings.Replace(s, "{{name}}", c.Name, -1)

	var items string
	for i := range c.Items {
		item := c.Items[i].String()
		item = strings.Replace(item, "{{link}}", c.Link, -1)
		items += item
	}
	s = strings.Replace(s, "{{items}}", items, 1)
	return s
}

type post struct {
	Time    time.Time
	Link    string
	Content string
	Images  []*image // list of urls
}

type image struct {
	Source  string
	Caption string
}

func (p *post) String() string {
	var template string
	switch outputMode {
	case "html":
		template = htmlItem
	case "rss":
		template = rssItem
	}

	var s string
	// time format: Mon Jan 2 15:04:05 -0700 MST 2006
	s = strings.Replace(template, "{{time}}", p.Time.Format("Mon, 2 Jan 2006 15:04:05 MST"), 2)
	s = strings.Replace(s, "{{content}}", p.Content, 1)
	var imgs string
	for i := range p.Images {
		imgs += `<a href="` + p.Images[i].Source + `"><img src="` + p.Images[i].Source + `" title="` + p.Images[i].Caption + `"></a>`
	}
	s = strings.Replace(s, "{{images}}", imgs, 1)

	return s
}

type handler struct{}

func (h handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	group := r.URL.Path[1:]
	if strings.HasSuffix(group, ".rss") {
		group = strings.TrimSuffix(group, ".rss")
		outputMode = "rss"
	}

	c, err := fetch(group)
	if err != nil {
		http.Error(w, fmt.Sprintf("error: %s", err), 400)
		return
	}

	if c == nil || len(c.Items) < 1 {
		http.Error(w, fmt.Sprintf("%s", "group not found"), 400)
		return
	}

	c.Name = group

	fmt.Fprintf(w, "%s\n", c.String())
}

func main() {
	outputMode = "html"
	fmt.Println("Serving: http://localhost:1212")
	http.ListenAndServe(":1212", handler{})
}

func fetch(group string) (c *channel, err error) {
	if group == "" {
		return
	}

	url := "https://www.facebook.com/pg/" + group + "/posts/"

	resp, err := http.Get(url)
	if err != nil {
		return
	}
	defer resp.Body.Close()

	c, err = parse(resp.Body)
	if err != nil {
		return
	}

	c.Link = url

	return
}