package main

// The plugin's SessionStart hook (novox/hq ADR 0489 §1, issue 1744): `claude-code session-start <waits-dir>`,
// run by the agent's own account on every start, resume, /clear and /compact. The tool runner never tells a
// session its own id (only a hook's stdin carries session_id), so a session cannot name itself to
// claude_code_wait until this hook has told it. It also lists the session's still-open waits, so a session
// that /clear-ed sees what it was watching before.
//
// It reads the session's mirrored waits file directly — the same local read the Stop hook makes
// (readWaitsFile, waits.go) — never calling back into this module: this hook runs on every start, and must
// not wait on the bus to do it. A missing or malformed file is not an error here: there is simply nothing
// open to report.

import (
	"encoding/json"
	"fmt"
	"io"
	"strings"
	"time"
)

// SessionStartInput is what the hook is given on stdin.
type SessionStartInput struct {
	SessionID string `json:"session_id"`
}

// SessionStartMessage is the line the hook prints: the session's id and how to give it to claude_code_wait,
// then each still-open wait from before (1744/AC1, AC2). Pure of IO beyond the one file read.
func SessionStartMessage(sessionID, waitsDir string, now time.Time) string {
	var b strings.Builder
	fmt.Fprintf(&b, "This session's id is %s; give it as `session` to claude_code_wait.\n", sessionID)
	f, err := readWaitsFile(waitsFileIn(waitsDir, sessionID))

	if err != nil || len(f.Waits) == 0 {
		return b.String()
	}
	b.WriteString("Waits still open from before this session's last start, resume, /clear or /compact:\n")
	for _, w := range f.Waits {
		age := now.Sub(w.At).Round(time.Second)
		state := "no watcher yet"
		if w.Watcher != "" {
			state = "watched"
		}
		if w.PastBound(now) {
			state += ", past its bound"
			if w.Said {
				state += ", said"
			}
		}
		fmt.Fprintf(&b, "  %s — %s (%s ago, %s)\n", w.ID, w.What, age, state)
	}
	return b.String()
}

// runSessionStart is the hook: the session's id and its open waits out, exit 0 always (1744/AC3).
func runSessionStart(waitsDir string, stdin io.Reader, stdout io.Writer) (code int) {
	defer func() {
		if recover() != nil {
			code = 0 // never fails the session's start
		}
	}()
	var in SessionStartInput
	if err := json.NewDecoder(stdin).Decode(&in); err != nil || strings.TrimSpace(in.SessionID) == "" {
		return 0
	}
	fmt.Fprint(stdout, SessionStartMessage(in.SessionID, waitsDir, time.Now()))
	return 0
}