// Command server is a browser chat playground for claude_pipe. It serves a small
// single-page chat UI and, for each message, launches `claude_pipe --stream` as a
// subprocess and relays its NDJSON events (text_delta + result) to the browser as
// Server-Sent Events. The browser renders the answer token-chunk by token-chunk.
//
// This proves the whole stack end to end through a real surface: the PTY capture,
// the VT render, the TUI parser (with the spinner fix), and the streaming delta —
// all driving a live chat in the browser.
//
// Each message is an independent one-shot claude session: claude_pipe does not keep
// conversation context between turns, so the chat has no memory across messages.
//
// Run:
//
//	cd apps/claude_pipe && CGO_ENABLED=1 go build -tags fts5 -o claude_pipe .
//	cd playground && go run ./web            # then open http://localhost:8099
package main

import (
	"bufio"
	_ "embed"
	"flag"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
)

//go:embed index.html
var indexHTML []byte

var (
	binPath string
	root    string
	warmup  string
	idle    string
	maxDur  string
)

func main() {
	port := flag.String("port", "8099", "port to listen on")
	bin := flag.String("bin", "/home/enmanuel/fn_registry/apps/claude_pipe/claude_pipe", "path to the claude_pipe binary")
	rootDir := flag.String("root", "/home/enmanuel/fn_registry", "cwd for claude (a repo whose MCP servers are approved)")
	wu := flag.String("warmup", "4s", "claude_pipe --warmup")
	id := flag.String("idle", "4s", "claude_pipe --idle")
	md := flag.String("max", "120s", "claude_pipe --max")
	flag.Parse()

	abs, err := filepath.Abs(*bin)
	if err != nil {
		log.Fatalf("resolve --bin: %v", err)
	}
	if _, err := os.Stat(abs); err != nil {
		log.Fatalf("claude_pipe binary not found at %s — build it first:\n  (cd .. && CGO_ENABLED=1 go build -tags fts5 -o claude_pipe .)", abs)
	}
	binPath, root, warmup, idle, maxDur = abs, *rootDir, *wu, *id, *md

	http.HandleFunc("/", handleIndex)
	http.HandleFunc("/chat", handleChat)

	addr := ":" + *port
	log.Printf("claude_pipe web chat → http://localhost:%s  (bin=%s root=%s)", *port, binPath, root)
	log.Fatal(http.ListenAndServe(addr, nil))
}

func handleIndex(w http.ResponseWriter, r *http.Request) {
	if r.URL.Path != "/" {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	_, _ = w.Write(indexHTML)
}

// handleChat runs claude_pipe --stream for the given prompt and relays each NDJSON
// line as a Server-Sent Event. The browser opens this via EventSource.
func handleChat(w http.ResponseWriter, r *http.Request) {
	prompt := r.URL.Query().Get("prompt")
	if prompt == "" {
		http.Error(w, "missing prompt", http.StatusBadRequest)
		return
	}

	flusher, ok := w.(http.Flusher)
	if !ok {
		http.Error(w, "streaming unsupported", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("X-Accel-Buffering", "no")

	// The request context is cancelled when the browser closes the EventSource;
	// CommandContext then kills the claude_pipe subprocess (and its PTY child).
	cmd := exec.CommandContext(r.Context(), binPath,
		"--stream",
		"--cwd", root,
		"--warmup", warmup,
		"--idle", idle,
		"--max", maxDur,
		prompt,
	)
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		sse(w, flusher, "error", fmt.Sprintf(`{"message":%q}`, err.Error()))
		return
	}
	cmd.Stderr = os.Stderr

	if err := cmd.Start(); err != nil {
		sse(w, flusher, "error", fmt.Sprintf(`{"message":%q}`, err.Error()))
		return
	}

	sc := bufio.NewScanner(stdout)
	sc.Buffer(make([]byte, 1024*1024), 1024*1024)
	for sc.Scan() {
		// Each line is already a JSON object ({"type":"text_delta",...} or result).
		// Relay it verbatim as the SSE data payload.
		sse(w, flusher, "", sc.Text())
	}
	_ = cmd.Wait()

	// Signal completion so the browser can close the stream.
	sse(w, flusher, "done", "{}")
}

// sse writes one Server-Sent Event. If event is empty, a default "message" event
// is emitted (what EventSource.onmessage receives).
func sse(w http.ResponseWriter, f http.Flusher, event, data string) {
	if event != "" {
		fmt.Fprintf(w, "event: %s\n", event)
	}
	fmt.Fprintf(w, "data: %s\n\n", data)
	f.Flush()
}