package main

import (
	"bytes"
	"embed"
	"flag"
	"fmt"
	"html/template"
	"io/ioutil"
	"log"
	"net/http"
	"strings"

	"gopkg.in/yaml.v3"
)

//go:embed templates
var tpls embed.FS

type repository struct {
	Name string `yaml:"name"`
	Repo string `yaml:"repo"`
}

type config struct {
	BaseUrl      string       `yaml:"baseUrl"`
	VCS          string       `yaml:"vcs"`
	Repositories []repository `yaml:"repositories"`
}

type moduleTmpl struct {
	Name    string
	Repo    string
	VCS     string
	BaseUrl string
}

func main() {
	flag.Parse()

	cfg, err := loadConfig()
	if err != nil {
		log.Fatal(err)
	}

	http.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(200)
		w.Write([]byte("ok"))
	})

	http.HandleFunc("/", goGet(cfg))

	log.Printf("starting web server on :8080")
	log.Fatal(http.ListenAndServe(":8080", nil))
}

func loadConfig() (*config, error) {
	configPath := "./vanity.yaml"

	configYaml, err := ioutil.ReadFile(configPath)
	if err != nil {
		return nil, fmt.Errorf("failed to read configuration file %s: %v", configPath, err)
	}

	var cfg config
	err = yaml.Unmarshal(configYaml, &cfg)
	if err != nil {
		return nil, fmt.Errorf("failed to unmarshall configuration: %v", err)
	}

	return &cfg, nil
}

func goGet(cfg *config) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			status := http.StatusMethodNotAllowed
			http.Error(w, http.StatusText(status), status)
			return
		}

		if r.FormValue("go-get") == "1" {
			pathParts := strings.Split(r.URL.Path, "/")
			for _, m := range cfg.Repositories {
				if pathParts[1] == m.Name {
					goGetModule(w, r, m, cfg)
					return
				}
			}
			status := http.StatusNotFound
			http.Error(w, http.StatusText(status), status)
			return
		}
		browserURL(w, r, cfg)
	}
}

func goGetModule(w http.ResponseWriter, r *http.Request, m repository, cfg *config) {
	tmpl, err := template.ParseFS(tpls, "templates/module.html.tpl")
	if err != nil {
		log.Fatal(err)
	}
	mod := moduleTmpl{
		VCS:     cfg.VCS,
		BaseUrl: cfg.BaseUrl,
		Name:    m.Name,
		Repo:    m.Repo,
	}
	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, mod); err != nil {
		log.Printf("error: %+v", err)
		status := http.StatusInternalServerError
		http.Error(w, http.StatusText(status), status)
	} else {
		w.Header().Set("Cache-Control", "no-store")
		w.Write(buf.Bytes())
	}
}

func browserURL(w http.ResponseWriter, r *http.Request, cfg *config) {
	tmpl, err := template.ParseFS(tpls, "templates/index.html.tpl")
	if err != nil {
		log.Fatal(err)
	}
	var buf bytes.Buffer
	if err := tmpl.Execute(&buf, cfg); err != nil {
		log.Printf("error: %+v", err)
		status := http.StatusInternalServerError
		http.Error(w, http.StatusText(status), status)
	} else {
		w.Header().Set("Cache-Control", "no-store")
		w.Write(buf.Bytes())
	}
}