// ollie-httpgw - HTTP gateway for the ollie 9P server.
//
// Maps HTTP methods to 9P file operations:
//
//	GET    /path  - read file content or list directory entries
//	PUT    /path  - write request body to file
//	POST   /path  - create file (name = last path element)
//	DELETE /path  - remove file
//	HEAD   /path  - stat file (metadata in headers)
//	PATCH  /path  - wstat (rename via JSON {"name": "newname"})
package main

import (
	_ "embed"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"path"
	"strings"

	"9fans.net/go/plan9"
	"9fans.net/go/plan9/client"
)

//go:embed openapi.json
var openapiSpec []byte

var (
	listen  = flag.String("listen", ":8080", "HTTP listen address")
	service = flag.String("service", "ollie", "9P service name to connect to")
	network = flag.String("net", "", "network type (unix, tcp); empty = use namespace")
	addr    = flag.String("addr", "", "9P server address; empty = use namespace service")
)

func main() {
	flag.Parse()
	http.HandleFunc("/openapi.json", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.Write(openapiSpec)
	})
	http.HandleFunc("/", handler)
	log.Printf("ollie-httpgw listening on %s", *listen)
	log.Fatal(http.ListenAndServe(*listen, nil))
}

func dial() (*client.Fsys, error) {
	if *addr != "" {
		n := *network
		if n == "" {
			n = "tcp"
		}
		return client.Mount(n, *addr)
	}
	return client.MountService(*service)
}

type dirEntry struct {
	Name  string `json:"name"`
	Size  uint64 `json:"size"`
	Mode  uint32 `json:"mode"`
	Mtime uint32 `json:"mtime"`
	IsDir bool   `json:"is_dir"`
}

func dirToEntry(d *plan9.Dir) dirEntry {
	return dirEntry{
		Name:  d.Name,
		Size:  d.Length,
		Mode:  uint32(d.Mode),
		Mtime: d.Mtime,
		IsDir: d.Mode&plan9.DMDIR != 0,
	}
}

func setStatHeaders(w http.ResponseWriter, d *plan9.Dir) {
	w.Header().Set("X-9p-Name", d.Name)
	w.Header().Set("X-9p-Size", fmt.Sprintf("%d", d.Length))
	w.Header().Set("X-9p-Mode", fmt.Sprintf("%o", d.Mode))
	w.Header().Set("X-9p-Mtime", fmt.Sprintf("%d", d.Mtime))
	if d.Mode&plan9.DMDIR != 0 {
		w.Header().Set("X-9p-Type", "dir")
	} else {
		w.Header().Set("X-9p-Type", "file")
	}
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(v)
}

func handler(w http.ResponseWriter, r *http.Request) {
	fsys, err := dial()
	if err != nil {
		writeJSON(w, http.StatusBadGateway, map[string]string{"error": "9p connect: " + err.Error()})
		return
	}
	defer fsys.Close()

	p := strings.TrimPrefix(r.URL.Path, "/")

	// Internal paths not exposed via HTTP.
	first, _, _ := strings.Cut(p, "/")
	switch first {
	case "", "a", "p", "m", "t", "sk", "help", "tr", "u", "x", "tmp":
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
		return
	}
	base := path.Base(p)
	switch base {
	case "systemprompt", "statewait":
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "not found"})
		return
	case "new":
		if r.Method == http.MethodPost {
			handleWrite(w, r, fsys, p)
			return
		}
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
		return
	}

	switch r.Method {
	case http.MethodGet:
		handleRead(w, fsys, p)
	case http.MethodHead:
		handleStat(w, fsys, p)
	case http.MethodPost:
		if base == "chat" {
			writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "chat is read-only"})
			return
		}
		handleWrite(w, r, fsys, p)
	case http.MethodDelete:
		handleRemove(w, fsys, p)
	case http.MethodPatch:
		handleWstat(w, r, fsys, p)
	case http.MethodOptions:
		handleOptions(w, r, p)
	default:
		writeJSON(w, http.StatusMethodNotAllowed, map[string]string{"error": "method not allowed"})
	}
}

var allowedMethods = "GET, HEAD, POST, DELETE, PATCH, OPTIONS"

var methodDescriptions = map[string]string{
	"GET":     "read file content or list directory entries",
	"HEAD":    "stat file (metadata in response headers)",
	"POST":    "write to file or trigger action",
	"DELETE":  "remove file or session",
	"PATCH":   "rename via JSON {\"name\": \"newname\"}",
	"OPTIONS": "describe available operations for this path",
}

func handleOptions(w http.ResponseWriter, _ *http.Request, p string) {
	w.Header().Set("Allow", allowedMethods)
	writeJSON(w, http.StatusOK, map[string]any{
		"path":    "/" + p,
		"methods": methodDescriptions,
	})
}

func handleRead(w http.ResponseWriter, fsys *client.Fsys, p string) {
	d, err := fsys.Stat(p)
	if err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": err.Error()})
		return
	}
	setStatHeaders(w, d)

	if d.Mode&plan9.DMDIR != 0 {
		fid, err := fsys.Open(p, plan9.OREAD)
		if err != nil {
			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
			return
		}
		defer fid.Close()
		dirs, err := fid.Dirreadall()
		if err != nil {
			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
			return
		}
		if p == "s" {
			var ids []string
			for _, de := range dirs {
				if de.Mode&plan9.DMDIR != 0 {
					ids = append(ids, de.Name)
				}
			}
			writeJSON(w, http.StatusOK, ids)
			return
		}
		entries := make([]dirEntry, len(dirs))
		for i, de := range dirs {
			entries[i] = dirToEntry(de)
		}
		writeJSON(w, http.StatusOK, entries)
		return
	}

	fid, err := fsys.Open(p, plan9.OREAD)
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	defer fid.Close()
	content, err := io.ReadAll(fid)
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	if p == "s/idx" {
		writeJSON(w, http.StatusOK, parseIdx(content))
		return
	}
	writeJSON(w, http.StatusOK, parseContent(content, path.Base(p)))
}

type idxEntry struct {
	ID      string `json:"id"`
	State   string `json:"state"`
	CWD     string `json:"cwd"`
	Backend string `json:"backend"`
	Model   string `json:"model"`
}

func parseIdx(data []byte) []idxEntry {
	var entries []idxEntry
	for line := range strings.SplitSeq(strings.TrimRight(string(data), "\n"), "\n") {
		if line == "" {
			continue
		}
		fields := strings.SplitN(line, "\t", 5)
		if len(fields) != 5 {
			continue
		}
		entries = append(entries, idxEntry{
			ID:      fields[0],
			State:   fields[1],
			CWD:     fields[2],
			Backend: fields[3],
			Model:   fields[4],
		})
	}
	return entries
}

// parseContent detects the wire format and returns the appropriate Go value:
//   - key=value lines → map[string]string
//   - tab-separated records → [][]string
//   - multiple newline-separated values → []string
//   - single value → map[string]string{name: value}
func parseContent(data []byte, name string) any {
	s := strings.TrimRight(string(data), "\n")
	if s == "" {
		return map[string]string{}
	}
	first, _, _ := strings.Cut(s, "\n")
	if strings.Contains(first, "=") {
		m := make(map[string]string)
		for line := range strings.SplitSeq(s, "\n") {
			if line == "" {
				continue
			}
			k, v, _ := strings.Cut(line, "=")
			m[k] = v
		}
		return m
	}
	if strings.Contains(first, "\t") {
		var rows [][]string
		for line := range strings.SplitSeq(s, "\n") {
			if line != "" {
				rows = append(rows, strings.Split(line, "\t"))
			}
		}
		return rows
	}
	var lines []string
	for line := range strings.SplitSeq(s, "\n") {
		if line != "" {
			lines = append(lines, line)
		}
	}
	if len(lines) == 1 {
		return map[string]string{name: lines[0]}
	}
	return lines
}

// serializeKV serializes a map to newline-separated key=value lines.
func serializeKV(m map[string]any) []byte {
	var sb strings.Builder
	for k, v := range m {
		fmt.Fprintf(&sb, "%s=%v\n", k, v)
	}
	return []byte(sb.String())
}

func handleStat(w http.ResponseWriter, fsys *client.Fsys, p string) {
	d, err := fsys.Stat(p)
	if err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": err.Error()})
		return
	}
	setStatHeaders(w, d)
	w.Header().Set("Content-Type", "application/json")
}

func handleWrite(w http.ResponseWriter, r *http.Request, fsys *client.Fsys, p string) {
	var m map[string]any
	if err := json.NewDecoder(r.Body).Decode(&m); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
		return
	}
	fid, err := fsys.Open(p, plan9.OWRITE)
	if err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": err.Error()})
		return
	}
	n, err := fid.Write(serializeKV(m))
	fid.Close()
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	writeJSON(w, http.StatusOK, map[string]int{"bytes_written": n})
}


func handleRemove(w http.ResponseWriter, fsys *client.Fsys, p string) {
	if err := fsys.Remove(p); err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": err.Error()})
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func handleWstat(w http.ResponseWriter, r *http.Request, fsys *client.Fsys, p string) {
	var req struct {
		Name string `json:"name"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
		return
	}
	d := &plan9.Dir{Name: req.Name}
	if err := fsys.Wstat(p, d); err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	w.WriteHeader(http.StatusNoContent)
}