package main

import (
	"context"
	"embed"
	"flag"
	"fmt"
	iofs "io/fs"
	"log"
	"net/http"
	"os"
	"os/signal"
	"path/filepath"
	"strings"
	"syscall"
	"text/tabwriter"
	"time"

	"fn-registry/functions/core"

	"dag-engine/store"
)

//go:embed all:frontend/dist
var frontendDist embed.FS

func main() {
	if len(os.Args) < 2 {
		printUsage()
		os.Exit(1)
	}

	cmd := os.Args[1]
	args := os.Args[2:]

	switch cmd {
	case "run":
		cmdRun(args)
	case "list":
		cmdList(args)
	case "status":
		cmdStatus(args)
	case "validate":
		cmdValidate(args)
	case "server":
		cmdServer(args)
	case "help", "-h", "--help":
		printUsage()
	default:
		fmt.Fprintf(os.Stderr, "unknown command: %s\n", cmd)
		printUsage()
		os.Exit(1)
	}
}

func printUsage() {
	fmt.Println(`dag-engine — DAG workflow executor

Usage:
  dag-engine <command> [options]

Commands:
  run <path.yaml>         Execute a DAG and show results
  list [dir]              List DAGs with schedule and last status
  status [dag_name]       Show execution history
  validate <path.yaml>    Parse and validate without executing
  server                  Start HTTP server with web frontend

Server options:
  --port <port>           HTTP port (default: 8090)
  --dags-dir <dir>        DAGs directory (default: ~/dagu/dags)
  --db <path>             SQLite database path (default: dag_engine.db)
  --scheduler             Auto-start cron scheduler`)
}

// --- CLI Commands ---

func cmdRun(args []string) {
	if len(args) < 1 {
		fmt.Fprintln(os.Stderr, "usage: dag-engine run <path.yaml>")
		os.Exit(1)
	}

	dagPath := args[0]
	cfg := DefaultConfig()

	// Parse optional flags after the path.
	fs := flag.NewFlagSet("run", flag.ExitOnError)
	fs.StringVar(&cfg.DBPath, "db", cfg.DBPath, "SQLite database path")
	fs.Parse(args[1:])

	db, err := store.Open(cfg.DBPath)
	if err != nil {
		log.Fatalf("open db: %v", err)
	}
	defer db.Close()

	executor := NewExecutor(db, filepath.Dir(dagPath))

	fmt.Printf("Executing %s...\n", dagPath)
	ctx := context.Background()
	runID, err := executor.ExecuteDAG(ctx, dagPath, "manual")

	// Print results.
	if runID != "" {
		run, _ := db.GetRun(runID)
		steps, _ := db.ListStepResults(runID)

		if run != nil {
			fmt.Println()
			for _, s := range steps {
				icon := "  "
				switch s.Status {
				case "success":
					icon = "OK"
				case "failed":
					icon = "!!"
				case "skipped":
					icon = "--"
				case "running":
					icon = ".."
				}
				fmt.Printf("[%s] %s (%dms)\n", icon, s.StepName, s.DurationMs)
				if s.Status == "failed" && s.Stderr != "" {
					for _, line := range strings.Split(strings.TrimSpace(s.Stderr), "\n") {
						fmt.Printf("     %s\n", line)
					}
				}
			}
			fmt.Println()

			dur := ""
			if run.FinishedAt != nil {
				dur = fmt.Sprintf(" (%s)", run.FinishedAt.Sub(run.StartedAt).Round(time.Millisecond))
			}
			fmt.Printf("Run %s: %s%s\n", runID, strings.ToUpper(run.Status), dur)
		}
	}

	if err != nil {
		os.Exit(1)
	}
}

func cmdList(args []string) {
	cfg := DefaultConfig()
	if len(args) > 0 && !strings.HasPrefix(args[0], "-") {
		cfg.DagsDir = args[0]
		args = args[1:]
	}

	fs := flag.NewFlagSet("list", flag.ExitOnError)
	fs.StringVar(&cfg.DBPath, "db", cfg.DBPath, "SQLite database path")
	fs.Parse(args)

	db, err := store.Open(cfg.DBPath)
	if err != nil {
		log.Fatalf("open db: %v", err)
	}
	defer db.Close()

	executor := NewExecutor(db, cfg.DagsDir)
	dags, err := executor.ListDAGs()
	if err != nil {
		log.Fatalf("list dags: %v", err)
	}

	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintln(w, "NAME\tSCHEDULE\tTYPE\tTAGS\tLAST STATUS\tLAST RUN")
	for _, d := range dags {
		sched := strings.Join(d.Schedule, ", ")
		tags := strings.Join(d.Tags, ", ")
		lastStatus := "-"
		lastRun := "-"
		if d.LastRun != nil {
			lastStatus = d.LastRun.Status
			lastRun = d.LastRun.StartedAt.Format("2006-01-02 15:04")
		}
		typ := d.Type
		if typ == "" {
			typ = "chain"
		}
		fmt.Fprintf(w, "%s\t%s\t%s\t%s\t%s\t%s\n", d.Name, sched, typ, tags, lastStatus, lastRun)
	}
	w.Flush()
}

func cmdStatus(args []string) {
	cfg := DefaultConfig()

	fs := flag.NewFlagSet("status", flag.ExitOnError)
	fs.StringVar(&cfg.DBPath, "db", cfg.DBPath, "SQLite database path")
	limit := fs.Int("limit", 10, "number of runs to show")
	fs.Parse(args)

	dagName := ""
	if fs.NArg() > 0 {
		dagName = fs.Arg(0)
	}

	db, err := store.Open(cfg.DBPath)
	if err != nil {
		log.Fatalf("open db: %v", err)
	}
	defer db.Close()

	runs, total, err := db.ListRuns(dagName, *limit, 0)
	if err != nil {
		log.Fatalf("list runs: %v", err)
	}

	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "Showing %d of %d runs", len(runs), total)
	if dagName != "" {
		fmt.Fprintf(w, " for %s", dagName)
	}
	fmt.Fprintln(w)
	fmt.Fprintln(w, "RUN_ID\tDAG\tSTATUS\tTRIGGER\tSTARTED\tDURATION")
	for _, r := range runs {
		dur := "-"
		if r.FinishedAt != nil {
			dur = r.FinishedAt.Sub(r.StartedAt).Round(time.Millisecond).String()
		}
		fmt.Fprintf(w, "%s\t%s\t%s\t%s\t%s\t%s\n",
			r.ID, r.DagName, r.Status, r.Trigger,
			r.StartedAt.Format("2006-01-02 15:04:05"), dur)
	}
	w.Flush()
}

func cmdValidate(args []string) {
	if len(args) < 1 {
		fmt.Fprintln(os.Stderr, "usage: dag-engine validate <path.yaml>")
		os.Exit(1)
	}

	data, err := os.ReadFile(args[0])
	if err != nil {
		log.Fatalf("read: %v", err)
	}

	dag, err := core.DagParse(data)
	if err != nil {
		log.Fatalf("parse error: %v", err)
	}

	result := core.DagValidate(dag)

	fmt.Printf("DAG: %s\n", dag.Name)
	fmt.Printf("Steps: %d\n", len(dag.Steps))
	fmt.Printf("Schedule: %v\n", dag.Schedule)
	fmt.Printf("Type: %s\n", dag.Type)

	if result.Valid {
		fmt.Println("Validation: PASS")
		for i, level := range result.Levels {
			fmt.Printf("  Level %d: %v\n", i, level)
		}
	} else {
		fmt.Println("Validation: FAIL")
		for _, e := range result.Errors {
			fmt.Printf("  ERROR: %s\n", e)
		}
	}
	for _, w := range result.Warnings {
		fmt.Printf("  WARNING: %s\n", w)
	}

	if !result.Valid {
		os.Exit(1)
	}
}

// --- Server Command ---

func cmdServer(args []string) {
	cfg := DefaultConfig()
	fs := flag.NewFlagSet("server", flag.ExitOnError)
	cfg.ParseFlags(fs, args)

	db, err := store.Open(cfg.DBPath)
	if err != nil {
		log.Fatalf("open db: %v", err)
	}
	defer db.Close()

	executor := NewExecutor(db, cfg.DagsDir)
	scheduler := NewScheduler(executor, cfg.DagsDir)

	// Prepare frontend FS.
	var feFS iofs.FS
	distFS, err := iofs.Sub(frontendDist, "frontend/dist")
	if err == nil {
		// Check if dist has content (built frontend exists).
		entries, _ := iofs.ReadDir(distFS, ".")
		if len(entries) > 0 {
			feFS = distFS
			log.Printf("serving frontend from embedded dist/")
		}
	}
	if feFS == nil {
		log.Printf("no frontend build found, API-only mode")
	}

	mux := http.NewServeMux()
	RegisterAPI(mux, executor, scheduler, feFS)

	handler := corsMiddleware(loggingMiddleware(mux))

	if cfg.AutoScheduler {
		if err := scheduler.Start(); err != nil {
			log.Printf("scheduler start: %v", err)
		}
	}

	addr := fmt.Sprintf(":%d", cfg.Port)
	log.Printf("dag-engine server starting on http://0.0.0.0%s", addr)
	log.Printf("dags dir: %s", cfg.DagsDir)
	log.Printf("database: %s", cfg.DBPath)

	srv := &http.Server{Addr: addr, Handler: handler}

	// Graceful shutdown.
	go func() {
		sigCh := make(chan os.Signal, 1)
		signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
		<-sigCh
		log.Println("shutting down...")
		scheduler.Stop()
		srv.Shutdown(context.Background())
	}()

	if err := srv.ListenAndServe(); err != http.ErrServerClosed {
		log.Fatalf("server: %v", err)
	}
}