package main

import (
  "log"
  "fmt"
  "bytes"
  "strings"
  "io/fs"
  "io"
  "path/filepath"
  "os"
  "flag"
  "time"
  "text/template"
  "git.learnjsthehardway.com/learn-code-the-hard-way/ssgod/config"
  "github.com/yuin/goldmark"
  "github.com/fsnotify/fsnotify"
)

var DEFAULT_CONFIG = `
views = "pages"
layout = "pages/layouts/main.html"
target = "public"
watch_delay = "500ms"
`

func Fail(err error, format string, v ...any) error {
  err_format := fmt.Sprintf("ERROR: %v; %s", err, format)
  log.Printf(err_format, v...)
  return err
}

func RenderTemplate(out io.Writer, embed string, variables any) (error) {
  layout_path := config.Settings.Layout

  layout_main, err := os.ReadFile(layout_path)

  if err != nil {
    return Fail(err, "can't read your layout file: %s", layout_path)
  }

  tmpl := template.New(layout_path)

  callbacks := template.FuncMap{
    "embed": func() string { return embed },
  }
  tmpl.Funcs(callbacks)

  tmpl, err = tmpl.Parse(string(layout_main))
  if err != nil { return Fail(err, "can't parse %s", layout_path) }

  err = tmpl.Execute(out, variables)

  return err
}

func RenderMarkdown(path string, target_path string, page_id string) error {
  log.Printf("MARKDOWN: %s -> %s", path, target_path)

  out, err := os.OpenFile(target_path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
  defer out.Close()

  if err != nil { return Fail(err, "writing file %s", target_path) }

  input_data, err := os.ReadFile(path)
  var md_out bytes.Buffer

  err = goldmark.Convert(input_data, &md_out)
  if err != nil { return Fail(err, "failed converting markdown %s", path) }

  err = RenderTemplate(out, md_out.String(),
            map[string]string{"PageId": page_id})

  if err != nil { return Fail(err, "failed to render template %s->%s", path, target_path) }

  return err;
}

func RenderHTML(source_path string, target_path string, page_id string) error {
  log.Printf("RENDER: %s -> %s", source_path, target_path)

  out, err := os.OpenFile(target_path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
  defer out.Close()

  html_content, err := os.ReadFile(source_path)
  if err != nil { return Fail(err, "cannot open html input %s", source_path) }

  err = RenderTemplate(out, string(html_content),
            map[string]string{"PageId": page_id})

  if err != nil { return Fail(err, "writing file %s", target_path) }

  return err;
}

func MkdirPath(target_path string) error {
  target_dir := filepath.Dir(target_path)
  _, err := os.Stat(target_dir)

  if os.IsNotExist(err) {
    log.Println("MAKING: ", target_dir)
    err = os.MkdirAll(target_dir, 0750)

    if err != nil { return Fail(err, "making path to %s", target_dir); }
  }

  return nil;
}

func SplitPathExt(path string) (string, string, bool) {
  split_path := strings.Split(path, string(os.PathSeparator))[1:]
  source_name := strings.Join(split_path, "/")  // Render wants / even on windows

  ext := filepath.Ext(source_name)
  source_name, found := strings.CutSuffix(source_name, ext)
  return source_name, ext, found
}

func RePrefixPath(path string, new_prefix string) string {
  split_path := strings.Split(path, string(os.PathSeparator))[1:]

  prefixed_path := append([]string{new_prefix}, split_path...)
  return filepath.Join(prefixed_path...)
}

func ProcessDirEntry(path string, d fs.DirEntry, err error) error  {
  settings := config.Settings

  if !d.IsDir() {
    if err != nil { return Fail(err, "path: %s", path); }

    source_name, ext, found := SplitPathExt(path)

    if found && path != settings.Layout {
      target_path := RePrefixPath(path, settings.Target)

      err = MkdirPath(target_path)
      if err != nil { return Fail(err, "making target path: %s", target_path) }

      // generate a data-testid for all pages based on template name
      page_id := strings.ReplaceAll(source_name, "/", "-") + "-page"

      if ext == ".html" {
        err = RenderHTML(path, target_path, page_id)

        if err != nil { return Fail(err, "failed to render %s", path) }
      } else if ext == ".md" {
        // need to strip the .md and replace with .html
        html_name, _ := strings.CutSuffix(target_path, ext)
        html_name = fmt.Sprintf("%s.html", html_name)

        RenderMarkdown(path, html_name, page_id)

        if err != nil { return Fail(err, "failed to render markdown %s", path) }
      }
    }
  }

  return nil
}

func RenderPages() {
  err := filepath.WalkDir(config.Settings.Views,
    func (path string, d fs.DirEntry, err error) error  {
        return ProcessDirEntry(path, d, err)
  })

  if err != nil { log.Fatalf("can't walk content") }
}

func WatchMatches(name string) bool {
  return filepath.Ext(name) == ".html" || filepath.Ext(name) == ".md"
}

func WatchDir() {
  watcher, err := fsnotify.NewWatcher()
  if err != nil { log.Fatal(err) }

  defer watcher.Close()

  wait_time, err := time.ParseDuration(config.Settings.WatchDelay)
  if err != nil { log.Fatal(err) }

  doit := time.NewTimer(wait_time)
  doit.Stop()

  go func() {
    for {
      select {
        case event, ok := <-watcher.Events:
          if !ok { return }
          log.Println("event: ", event)

          if WatchMatches(event.Name) {
            log.Println("modified file: ", event.Name)
            doit.Reset(wait_time)
          }
        case <-doit.C:
          RenderPages()
        case err, ok := <-watcher.Errors:
          if !ok { return }
          log.Println("error: ", err)
      }
    }
  }()

  err = filepath.WalkDir(config.Settings.Views,
    func (path string, d fs.DirEntry, err error) error  {
      if d.IsDir() {
        log.Println("WATCHING: ", path)
        err = watcher.Add(path)
        if err != nil { return Fail(err, "failed to watch %s", path) }
      }

      return nil
  })

  if err != nil { log.Fatalf("can't walk content") }

  <-make(chan struct{})
}

func InitConfig(config_file string) {
  _, err := os.Stat(config_file)

  if os.IsNotExist(err) {
    out, err := os.OpenFile(config_file, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0644)
    if err != nil { log.Fatalf("error opening %s", config_file) }
    defer out.Close()
    out.WriteString(DEFAULT_CONFIG)
  } else {
    log.Fatalf("there's already a %s file here", config_file);
  }
}

func main() {
  var config_file string

  flag.StringVar(&config_file, "config", "ssgod.toml", ".toml config file to use")
  flag.Parse()
  command := flag.Arg(0)

  switch command {
  case "watch":
    config.Load(config_file)
    WatchDir()
  case "init":
    InitConfig(config_file)
  default:
    config.Load(config_file)
    RenderPages();
  }
}