package server

import (
	"errors"
	"fes/modules/config"
	"fes/modules/ui"
	"fmt"
	"html/template"
	"io/fs"
	"net/http"
	"os"
	"path"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/pelletier/go-toml/v2"
	lua "github.com/yuin/gopher-lua"
)

/* this is the request data we pass over the bus to the application, via the fes.bus interface */
type reqData struct {
	path   string
	params map[string]string
}

/* performs relavent handling based on the directory passaed
 *
 * Special directories
 *  - www/     <= contains lua routes.
 *  - static/  <= static content accessable at /static/path or /static/dir/path.
 *  - include/ <= globally accessable lua functions, cannot directly access "fes" right now.
 *  - archive/ <= contains user facing files such as archives or dists.
 *
 */
func handleDir(entries []os.DirEntry, dir string, routes map[string]string, base string, isStatic bool) error {
	for _, entry := range entries {
		path := filepath.Join(dir, entry.Name())
		if entry.IsDir() {
			nextBase := joinBase(base, entry.Name())
			subEntries, err := os.ReadDir(path)
			if err != nil {
				return fmt.Errorf("failed to read directory %s: %w", path, err)
			}
			if err := handleDir(subEntries, path, routes, nextBase, isStatic); err != nil {
				return err
			}
			continue
		}
		route := joinBase(base, entry.Name())
		if !isStatic && strings.HasSuffix(entry.Name(), ".lua") {
			name := strings.TrimSuffix(entry.Name(), ".lua")
			if name == "index" {
				routes[basePath(base)] = path
				routes[route] = path
				continue
			}
			route = joinBase(base, name)
		} else if !isStatic && strings.HasSuffix(entry.Name(), ".md") {
			name := strings.TrimSuffix(entry.Name(), ".md")
			if name == "index" {
				routes[basePath(base)] = path
				routes[route] = path
				continue
			}
			route = joinBase(base, name)
		}
		routes[route] = path
	}
	return nil
}

// TODO(vx-clutch): this should not be a function
func loadIncludeModules(L *lua.LState, includeDir string) *lua.LTable {
	app := L.NewTable()
	ents, err := os.ReadDir(includeDir)
	if err != nil {
		return app
	}
	for _, e := range ents {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".lua") {
			continue
		}
		base := strings.TrimSuffix(e.Name(), ".lua")
		path := filepath.Join(includeDir, e.Name())
		if _, err := os.Stat(path); err != nil {
			tbl := L.NewTable()
			tbl.RawSetString("error", lua.LString(fmt.Sprintf("file not found: %s", path)))
			app.RawSetString(base, tbl)
			continue
		}
		if err := L.DoFile(path); err != nil {
			tbl := L.NewTable()
			tbl.RawSetString("error", lua.LString(err.Error()))
			app.RawSetString(base, tbl)
			continue
		}
		val := L.Get(-1)
		L.Pop(1)
		tbl, ok := val.(*lua.LTable)
		if !ok || tbl == nil {
			tbl = L.NewTable()
		}
		app.RawSetString(base, tbl)
	}
	return app
}

/* renders the given lua route */
func renderRoute(entry string, cfg *config.AppConfig, requestData reqData) ([]byte, error) {
	L := lua.NewState()
	defer L.Close()

	libFiles, err := fs.ReadDir(config.Lib, "lib")
	if err == nil {
		for _, de := range libFiles {
			if de.IsDir() || !strings.HasSuffix(de.Name(), ".lua") {
				continue
			}
			path := filepath.Join("lib", de.Name())
			fileData, err := config.Lib.ReadFile(path)
			if err != nil {
				continue
			}
			L.DoString(string(fileData))
		}
	}

	preloadLuaModule := func(name, path string) {
		L.PreloadModule(name, func(L *lua.LState) int {
			fileData, err := config.Lib.ReadFile(path)
			if err != nil {
				panic(err)
			}
			if err := L.DoString(string(fileData)); err != nil {
				panic(err)
			}
			L.Push(L.Get(-1))
			return 1
		})
	}

	preloadLuaModule("lib.std", "lib/std.lua")
	preloadLuaModule("lib.symbol", "lib/symbol.lua")
	preloadLuaModule("lib.util", "lib/util.lua")

	L.PreloadModule("fes", func(L *lua.LState) int {
		mod := L.NewTable()
		libModules := []string{}
		if ents, err := fs.ReadDir(config.Lib, "lib"); err == nil {
			for _, e := range ents {
				if e.IsDir() || !strings.HasSuffix(e.Name(), ".lua") {
					continue
				}
				libModules = append(libModules, strings.TrimSuffix(e.Name(), ".lua"))
			}
		}
		for _, modName := range libModules {
			path := filepath.Join("lib", modName+".lua")
			fileData, err := config.Lib.ReadFile(path)
			if err != nil {
				continue
			}
			if err := L.DoString(string(fileData)); err != nil {
				continue
			}
			val := L.Get(-1)
			L.Pop(1)
			tbl, ok := val.(*lua.LTable)
			if !ok || tbl == nil {
				tbl = L.NewTable()
			}
			if modName == "fes" {
				tbl.ForEach(func(k, v lua.LValue) { mod.RawSet(k, v) })
			} else {
				mod.RawSetString(modName, tbl)
			}
		}

		mod.RawSetString("app", loadIncludeModules(L, filepath.Join(".", "include")))

		if cfg != nil {
			site := L.NewTable()
			site.RawSetString("version", lua.LString(cfg.App.Version))
			site.RawSetString("name", lua.LString(cfg.App.Name))
			authors := L.NewTable()
			for i, a := range cfg.App.Authors {
				authors.RawSetInt(i+1, lua.LString(a))
			}
			site.RawSetString("authors", authors)
			mod.RawSetString("site", site)
		}

		bus := L.NewTable()
		bus.RawSetString("url", lua.LString(requestData.path))
		params := L.NewTable()
		for k, v := range requestData.params {
			params.RawSetString(k, lua.LString(v))
		}
		bus.RawSetString("params", params)
		mod.RawSetString("bus", bus)

		mod.RawSetString("markdown_to_html", L.NewFunction(func(L *lua.LState) int {
			L.Push(lua.LString(markdownToHTML(L.ToString(1))))
			return 1
		}))

		L.Push(mod)
		return 1
	})

	if err := L.DoFile(entry); err != nil {
		return []byte(""), err
	}

	if L.GetTop() == 0 {
		return []byte(""), nil
	}

	L.SetGlobal("__fes_result", L.Get(-1))
	if err := L.DoString("return tostring(__fes_result)"); err != nil {
		L.GetGlobal("__fes_result")
		if s := L.ToString(-1); s != "" {
			return []byte(s), nil
		}
		return []byte(""), nil
	}

	if s := L.ToString(-1); s != "" {
		return []byte(s), nil
	}
	return []byte(""), nil
}

/* this indexes and generate the page for viewing the archive directory */
func generateArchiveIndex(fsPath string, urlPath string) (string, error) {
	info, err := os.Stat(fsPath)
	if err != nil {
		return "", err
	}
	if !info.IsDir() {
		return "", fmt.Errorf("not a directory")
	}
	ents, err := os.ReadDir(fsPath)
	if err != nil {
		return "", err
	}
	type entryInfo struct {
		name  string
		isDir bool
		href  string
		size  int64
		mod   time.Time
	}
	var list []entryInfo
	for _, e := range ents {
		n := e.Name()
		full := filepath.Join(fsPath, n)
		st, err := os.Stat(full)
		if err != nil {
			continue
		}
		isd := st.IsDir()
		displayName := n
		if isd {
			displayName = n + "/"
		}
		href := path.Join(urlPath, n)
		if isd && !strings.HasSuffix(href, "/") {
			href = href + "/"
		}
		size := int64(-1)
		if !isd {
			size = st.Size()
		}
		list = append(list, entryInfo{name: displayName, isDir: isd, href: href, size: size, mod: st.ModTime()})
	}
	sort.Slice(list, func(i, j int) bool {
		if list[i].isDir != list[j].isDir {
			return list[i].isDir
		}
		return strings.ToLower(list[i].name) < strings.ToLower(list[j].name)
	})

	urlPath = basePath(strings.TrimPrefix(urlPath, "/archive"))

	var b strings.Builder

	b.WriteString("<html>\n<head><title>Index of ")
	b.WriteString(template.HTMLEscapeString(urlPath))
	b.WriteString("</title></head>\n<body>\n<h1>Index of ")
	b.WriteString(template.HTMLEscapeString(urlPath))
	b.WriteString("</h1><hr><pre>")

	if urlPath != "/" {
		b.WriteString(
			`<a href="/archive` +
				template.HTMLEscapeString(path.Dir(strings.TrimSuffix(urlPath, "/"))) +
				`">../</a>` + "\n",
		)
	} else {
		b.WriteString(
			`<a href="/">../</a>` + "\n",
		)
	}

	nameCol := 50
	for _, ei := range list {
		escapedName := template.HTMLEscapeString(ei.name)
		dateStr := ei.mod.Local().Format("02-Jan-2006 15:04")
		var sizeStr string
		if ei.isDir {
			sizeStr = "-"
		} else {
			sizeStr = fmt.Sprintf("%d", ei.size)
		}
		spaces := 1
		if len(escapedName) < nameCol {
			spaces = nameCol - len(escapedName)
		}
		line := `<a href="` + template.HTMLEscapeString(ei.href) + `">` + escapedName + `</a>` + strings.Repeat(" ", spaces) + dateStr + strings.Repeat(" ", 19-len(sizeStr)) + sizeStr + "\n"
		b.WriteString(line)
	}
	b.WriteString("</pre><hr></body>\n</html>")
	return b.String(), nil
}

/* generates the data for the not found page. Checks for user-defined source in this order
 * 404.lua => 404.md => 404.html => default.
 */
func generateNotFoundData(cfg *config.AppConfig) []byte {
	notFoundData := []byte(`
<html>
<head><title>404 Not Found</title></head>
<body>
<center><h1>404 Not Found</h1></center>
<hr><center>fes</center>
</body>
</html>
`)
	if _, err := os.Stat(filepath.Join("www", "404.lua")); err == nil {
		if nf, err := renderRoute("www/404.lua", cfg, reqData{}); err == nil {
			notFoundData = nf
		}
	} else if _, err := os.Stat("www/404.md"); err == nil {
		if buf, err := os.ReadFile("www/404.html"); err == nil {
			notFoundData = []byte(markdownToHTML(string(buf)))
		}
	} else if _, err := os.Stat("www/404.html"); err == nil {
		if buf, err := os.ReadFile("www/404.html"); err == nil {
			notFoundData = buf
		}
	}
	return notFoundData
}

/* helper to load all special directories */
func loadDirs() map[string]string {
	routes := make(map[string]string)

	if entries, err := os.ReadDir("www"); err == nil {
		if err := handleDir(entries, "www", routes, "", false); err != nil {
			ui.Warning("failed to handle www directory", err)
		}
	}

	if entries, err := os.ReadDir("static"); err == nil {
		if err := handleDir(entries, "static", routes, "/static", true); err != nil {
			ui.Warning("failed to handle static directory", err)
		}
	}

	if entries, err := os.ReadDir("archive"); err == nil {
		if err := handleDir(entries, "archive", routes, "/archive", true); err != nil {
			ui.Warning("failed to handle archive directory", err)
		}
	}

	return routes
}

/* helper to parse the Fes.toml and generate config */
func parseConfig() config.AppConfig {
	defaultCfg := config.AppConfig{}
	defaultCfg.App.Authors = []string{"unknown"}
	defaultCfg.App.Name = "unknown"
	defaultCfg.App.Version = "unknown"

	tomlDocument, err := os.ReadFile("Fes.toml")
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			ui.WARN("no config file found, using the default config. In order to specify a config file write to Fes.toml")
			return defaultCfg
		} else {
			ui.Error("failed to read Fes.toml", err)
			os.Exit(1)
		}
	}
	docStr := fixMalformedToml(string(tomlDocument))
	var cfg config.AppConfig
	if err := toml.Unmarshal([]byte(docStr), &cfg); err != nil {
		ui.Warning("failed to parse Fes.toml", err)
		cfg = defaultCfg
	}
	return cfg
}

/* helper to read the archive files */
func readArchive(w http.ResponseWriter, route string) error {
	fsPath := "." + route
	if info, err := os.Stat(fsPath); err == nil && info.IsDir() {
		if page, err := generateArchiveIndex(fsPath, route); err == nil {
			w.Write([]byte(page))
			return nil
		} else {
			return err
		}
	}
	return nil
}

/* start the Fes server */
func Start(dir string) error {
	if err := os.Chdir(dir); err != nil {
		return ui.Error(fmt.Sprintf("failed to change directory to %s", dir), err)
	}

	ui.Log("Running root=%s, port=%d.", filepath.Clean(dir), *config.Port)

	cfg := parseConfig()
	notFoundData := generateNotFoundData(&cfg)
	routes := loadDirs()

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		route, ok := routes[r.URL.Path]

		var err error = nil

		/* defer won't update paramaters unless we do this. */
		defer func() {
			ui.Path(route, err)
		}()

		if !ok {
			err = config.ErrRouteMiss
			route = r.URL.Path

			if strings.HasPrefix(route, "/archive") {
				err = readArchive(w, route)
			} else {
				w.WriteHeader(http.StatusNotFound)
				w.Write([]byte(notFoundData))
			}
			return
		}

		params := make(map[string]string)
		for k, v := range r.URL.Query() {
			if len(v) > 0 {
				params[k] = v[0]
			}
		}

		var data []byte
		if strings.HasSuffix(route, ".lua") {
			data, err = renderRoute(route, &cfg, reqData{path: r.URL.Path, params: params})
		} else if strings.HasSuffix(route, ".md") {
			data, err = os.ReadFile(route)
			data = []byte(markdownToHTML(string(data)))
			data = []byte("<style>body {max-width: 80ch;}</style>\n" + string(data))
		} else {
			data, err = os.ReadFile(route)
		}

		if err != nil {
			http.Error(w, fmt.Sprintf("Error loading page: %v", err), http.StatusInternalServerError)
		}

		w.Write(data)
	})
	ui.Log("Server initialized")

	ui.Log("Ready to accept connections tcp")
	return http.ListenAndServe(fmt.Sprintf("0.0.0.0:%d", *config.Port), nil)
}
