// Package main is the entry point for the agentctl binary.
// agentctl is a sidecar process that manages agent subprocess communication
// via HTTP API, bridging the agent's ACP protocol with the kandev backend.
//
// agentctl is runtime-agnostic - it behaves identically whether running
// inside a Docker container or directly on the host machine. The caller
// (kandev backend) handles any Docker vs standalone differences.
package main

import (
	"context"
	"flag"
	"fmt"
	"net"
	"net/http"
	"os"
	"os/signal"
	"strconv"
	"syscall"
	"time"

	"github.com/kandev/kandev/internal/agentctl/server/adapter/transport/shared"
	"github.com/kandev/kandev/internal/agentctl/server/api"
	"github.com/kandev/kandev/internal/agentctl/server/config"
	"github.com/kandev/kandev/internal/agentctl/server/instance"
	"github.com/kandev/kandev/internal/agentctl/server/process"
	"github.com/kandev/kandev/internal/common/logger"
	mcpserver "github.com/kandev/kandev/internal/mcp/server"
	"github.com/kandev/kandev/pkg/agent"
	"go.uber.org/zap"
)

// Command-line flags
var (
	protocolFlag     = flag.String("protocol", "", "Protocol for agent communication (acp, codex, mcp)")
	agentCommandFlag = flag.String("agent-command", "", "Command to run the agent")
	workDirFlag      = flag.String("workdir", "", "Working directory for the agent")
	portFlag         = flag.Int("port", 0, "HTTP server port")
)

func main() {
	// Dispatch kandev CLI subcommands before flag parsing or server startup.
	// When invoked as "agentctl kandev <cmd>", this runs the CLI and exits
	// without starting the HTTP server.
	if len(os.Args) > 1 && os.Args[1] == "kandev" {
		os.Exit(runKandevCLI(os.Args[2:]))
	}

	flag.Parse()

	// Load configuration
	cfg := config.Load()

	// Override with CLI flags if provided
	if *protocolFlag != "" {
		cfg.Defaults.Protocol = agent.Protocol(*protocolFlag)
	}
	if *agentCommandFlag != "" {
		cfg.Defaults.AgentCommand = *agentCommandFlag
	}
	if *workDirFlag != "" {
		cfg.Defaults.WorkDir = *workDirFlag
	}
	if *portFlag != 0 {
		cfg.Port = *portFlag
	}

	// Initialize logger
	log, err := logger.NewLogger(logger.LoggingConfig{
		Level:      cfg.LogLevel,
		Format:     cfg.LogFormat,
		OutputPath: "stdout",
	})
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to initialize logger: %v\n", err)
		os.Exit(1)
	}
	defer func() {
		_ = log.Sync()
	}()

	log.Info("starting agentctl",
		zap.Int("port", cfg.Port),
		zap.String("log_level", cfg.LogLevel))

	run(cfg, log)
}

// run starts the agentctl server.
// All instances are managed through the instance management API.
func run(cfg *config.Config, log *logger.Logger) {
	// Start the ACP debug-log janitor (no-op unless KANDEV_DEBUG_AGENT_MESSAGES
	// is set). It periodically flushes the per-session debug writers and prunes
	// old/oversized files so an always-on debug session can't fill the disk.
	acpJanitor := shared.NewACPJanitor()
	acpJanitor.Start(context.Background())

	// Create instance manager
	instMgr := instance.NewManager(cfg, log)

	// Set the server factory to create API servers for each instance
	instMgr.SetServerFactory(func(instCfg *config.InstanceConfig, procMgr *process.Manager, instLog *logger.Logger) http.Handler {
		// Create MCP backend client for bidirectional communication through agent stream
		// MCP requests from agents are sent through the agent stream WebSocket to the backend
		mcpBackendClient := mcpserver.NewChannelBackendClient(instLog)

		// Create MCP server using the channel-based backend client
		mcpSrv := mcpserver.New(mcpBackendClient, instCfg.SessionID, instCfg.TaskID, instCfg.Port, instLog, cfg.McpLogFile, instCfg.DisableAskQuestion, instCfg.McpMode)
		instLog.Info("MCP server enabled (channel-based)",
			zap.String("session_id", instCfg.SessionID))

		return api.NewServer(instCfg, procMgr, mcpSrv, mcpBackendClient, instLog).Router()
	})

	// Create control server
	controlServer := api.NewControlServer(cfg, instMgr, log)

	// Start HTTP server
	addr := fmt.Sprintf(":%d", cfg.Port)
	httpServer := &http.Server{
		Addr:    addr,
		Handler: controlServer.Router(),
	}

	go func() {
		log.Info("HTTP server starting", zap.String("address", addr))
		// Try to listen first so we get a clear error before serving
		ln, listenErr := net.Listen("tcp", addr)
		if listenErr != nil {
			log.Error("HTTP server failed to bind",
				zap.String("address", addr),
				zap.Error(listenErr))
			os.Exit(1)
		}
		log.Info("HTTP server bound successfully", zap.String("address", ln.Addr().String()))
		if err := httpServer.Serve(ln); err != nil && err != http.ErrServerClosed {
			log.Error("HTTP server error", zap.Error(err))
			os.Exit(1)
		}
	}()

	// Monitor parent liveness via inherited pipe (standalone mode only).
	// Returns a channel that closes when the parent dies.
	parentDied := monitorParentLiveness(log)

	// Wait for shutdown signal (OS signal or parent death)
	waitForShutdown(log, parentDied, func(ctx context.Context) {
		// Flush pending traces before stopping instances
		if err := shared.ShutdownTracing(ctx); err != nil {
			log.Error("error shutting down tracing", zap.Error(err))
		}
		// Shutdown all instances first so any final ACP frames they emit during
		// teardown are still captured by the (still-live) debug writers.
		if err := instMgr.Shutdown(ctx); err != nil {
			log.Error("error shutting down instance manager", zap.Error(err))
		}
		// Then flush + close all debug-log writers as the final logging step.
		acpJanitor.Stop()
		if err := httpServer.Shutdown(ctx); err != nil {
			log.Error("error shutting down HTTP server", zap.Error(err))
		}
	})
}

// waitForShutdown waits for a shutdown trigger (OS signal or parent death) and
// runs the cleanup function. parentDied may be nil when no parent monitor is active.
func waitForShutdown(log *logger.Logger, parentDied <-chan struct{}, cleanup func(ctx context.Context)) {
	sigCh := make(chan os.Signal, 1)
	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)

	if parentDied == nil {
		// No parent monitor — wait for OS signal only.
		sig := <-sigCh
		log.Info("received signal", zap.String("signal", sig.String()))
	} else {
		select {
		case sig := <-sigCh:
			log.Info("received signal", zap.String("signal", sig.String()))
		case <-parentDied:
			log.Warn("parent process died, initiating shutdown")
		}
	}

	log.Info("shutting down agentctl...")

	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
	defer cancel()

	cleanup(ctx)

	log.Info("agentctl stopped")
}

// monitorParentLiveness watches a pipe inherited from the parent process.
// The parent (kandev backend) passes the read-end of a pipe via ExtraFiles
// and sets KANDEV_PARENT_PIPE_FD to the FD number. A goroutine blocks on
// reading the pipe. When the parent dies — even via SIGKILL — the kernel
// closes the write-end, the read returns, and the returned channel is closed.
// Returns nil when the env var is absent (Docker, manual start, remote executors).
func monitorParentLiveness(log *logger.Logger) <-chan struct{} {
	fdStr := os.Getenv("KANDEV_PARENT_PIPE_FD")
	if fdStr == "" {
		return nil
	}

	fd, err := strconv.Atoi(fdStr)
	if err != nil {
		log.Warn("invalid KANDEV_PARENT_PIPE_FD", zap.String("value", fdStr), zap.Error(err))
		return nil
	}

	pipe := os.NewFile(uintptr(fd), "parent-liveness-pipe")
	if pipe == nil {
		log.Warn("failed to open parent liveness pipe", zap.Int("fd", fd))
		return nil
	}

	log.Info("parent liveness monitor started", zap.Int("fd", fd))

	ch := make(chan struct{})
	go func() {
		buf := make([]byte, 1)
		_, _ = pipe.Read(buf) // blocks until pipe breaks
		_ = pipe.Close()
		close(ch)
	}()

	return ch
}