package main

import (
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	tea "github.com/charmbracelet/bubbletea"
)

// findSubagentsDir searches ~/.claude/projects for a session ID prefix
// and returns the subagents directory path.
func findSubagentsDir(sessionPrefix string) (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("cannot determine home directory: %w", err)
	}

	projectsRoot := filepath.Join(home, ".claude", "projects")

	// Walk project dirs looking for a session dir matching the prefix
	projectDirs, err := os.ReadDir(projectsRoot)
	if err != nil {
		return "", fmt.Errorf("cannot read %s: %w", projectsRoot, err)
	}

	for _, pd := range projectDirs {
		if !pd.IsDir() {
			continue
		}
		projectPath := filepath.Join(projectsRoot, pd.Name())
		sessionDirs, err := os.ReadDir(projectPath)
		if err != nil {
			continue
		}
		for _, sd := range sessionDirs {
			if !sd.IsDir() {
				continue
			}
			if strings.HasPrefix(sd.Name(), sessionPrefix) {
				subagents := filepath.Join(projectPath, sd.Name(), "subagents")
				if info, err := os.Stat(subagents); err == nil && info.IsDir() {
					return subagents, nil
				}
			}
		}
	}

	return "", fmt.Errorf("no subagents directory found for session %q", sessionPrefix)
}

func main() {
	sessionFlag := flag.String("s", "", "Session ID prefix. Searches ~/.claude/projects for matching subagents directory.")
	listSessions := flag.Bool("ls", false, "List all sessions and exit.")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "Usage: agent-tui [flags] [directory]\n\n")
		fmt.Fprintf(os.Stderr, "Tail Claude Code subagent JSONL logs with a terminal UI.\n\n")
		fmt.Fprintf(os.Stderr, "  agent-tui -s 1f02          Find session by ID prefix\n")
		fmt.Fprintf(os.Stderr, "  agent-tui ./subagents/     Watch a specific directory\n")
		fmt.Fprintf(os.Stderr, "  agent-tui -ls ./subagents/ List sessions in directory\n\n")
		fmt.Fprintf(os.Stderr, "Flags:\n")
		flag.PrintDefaults()
	}
	flag.Parse()

	var dir string

	if *sessionFlag != "" && flag.NArg() == 0 {
		// Session ID mode: find the subagents dir automatically
		found, err := findSubagentsDir(*sessionFlag)
		if err != nil {
			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
			os.Exit(1)
		}
		dir = found
		fmt.Fprintf(os.Stderr, "Found: %s\n", dir)
	} else {
		// Directory mode
		dir = "."
		if flag.NArg() > 0 {
			dir = flag.Arg(0)
		}

		// Verify directory exists
		info, err := os.Stat(dir)
		if err != nil || !info.IsDir() {
			fmt.Fprintf(os.Stderr, "Error: %q is not a valid directory\n", dir)
			os.Exit(1)
		}
	}

	// Discover sessions
	sessions, err := DiscoverSessions(dir)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error scanning sessions: %v\n", err)
		os.Exit(1)
	}

	if len(sessions) == 0 {
		fmt.Fprintf(os.Stderr, "No JSONL files found in %q\n", dir)
		os.Exit(1)
	}

	// List sessions mode
	if *listSessions {
		fmt.Printf("Sessions in %s:\n\n", dir)
		for i, s := range sessions {
			marker := "  "
			if i == 0 {
				marker = "→ "
			}
			fmt.Printf("%s%-8s  %d agents  %4d events  %s – %s\n",
				marker,
				shortSessionID(s.ID),
				s.AgentCount,
				s.EventCount,
				s.FirstSeen.Format("15:04:05"),
				s.LastSeen.Format("15:04:05"),
			)
			for agentID, slug := range s.Agents {
				fmt.Printf("    agent %s (%s)\n", agentID[:min(7, len(agentID))], slug)
			}
		}
		fmt.Printf("\n(→ = most recent, used by default)\n")
		return
	}

	// Select session — when using -s to find the dir, there's typically
	// only one session per subagents dir, so just use the first
	activeSession := sessions[0].ID

	watcher := NewWatcher(dir)
	if err := watcher.Start(); err != nil {
		fmt.Fprintf(os.Stderr, "Error starting watcher: %v\n", err)
		os.Exit(1)
	}

	m := newModel(dir, sessions, activeSession)
	m.watcher = watcher

	// Load initial events in bulk (already sorted by timestamp)
	for _, evt := range watcher.InitialEvents() {
		m.handleNewEvent(evt)
	}

	p := tea.NewProgram(
		m,
		tea.WithAltScreen(),
		tea.WithMouseCellMotion(),
	)

	if _, err := p.Run(); err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		os.Exit(1)
	}
}