package mcp

import (
	"context"
	"encoding/json"
	"os"
	"path/filepath"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// writePending drops a raw/ note whose created_at is age old.
func writePending(t *testing.T, brainDir, name string, age time.Duration, now time.Time) {
	t.Helper()
	raw := filepath.Join(brainDir, "raw")
	require.NoError(t, os.MkdirAll(raw, 0o755))
	body := "---\ncreated_at: " + now.Add(-age).UTC().Format(time.RFC3339) + "\n---\n\nnote body\n"
	require.NoError(t, os.WriteFile(filepath.Join(raw, name), []byte(body), 0o644))
}

func TestPendingNudge_SilentWhenNothingIsPending(t *testing.T) {
	// No queue, no nudge. A notice that fires every session is one people
	// learn to skip, which is how the queue got ignored for three months in
	// the first place (#82).
	got := pendingNudge(t.TempDir(), time.Now(), 14*24*time.Hour)
	assert.Nil(t, got)
}

func TestPendingNudge_SilentWhileEverythingIsBelowTheThreshold(t *testing.T) {
	now := time.Now()
	dir := t.TempDir()
	writePending(t, dir, "fresh.md", 2*24*time.Hour, now)

	got := pendingNudge(dir, now, 14*24*time.Hour)
	assert.Nil(t, got, "a two-day-old note is not aging")
}

func TestPendingNudge_ReportsCountAndOldestAgeOnceSomethingAges(t *testing.T) {
	now := time.Now()
	dir := t.TempDir()
	writePending(t, dir, "old.md", 100*24*time.Hour, now)
	writePending(t, dir, "older.md", 120*24*time.Hour, now)
	writePending(t, dir, "fresh.md", 1*24*time.Hour, now)

	got := pendingNudge(dir, now, 14*24*time.Hour)
	require.NotNil(t, got)

	// All three are pending; the threshold decides whether to speak, not
	// what to count. Someone opening the queue sees the whole queue.
	assert.Equal(t, 3, got.Pending)
	assert.Equal(t, 2, got.Aging)
	assert.Equal(t, 120, got.OldestDays)
	assert.Equal(t, "older.md", got.Oldest)
}

func TestPendingNudge_NeverDecidesAnything(t *testing.T) {
	// Aging is a trigger to ask a human, never a verdict. The nudge must
	// carry no action and must leave the queue exactly as it found it.
	now := time.Now()
	dir := t.TempDir()
	writePending(t, dir, "ancient.md", 365*24*time.Hour, now)

	before, err := os.ReadDir(filepath.Join(dir, "raw"))
	require.NoError(t, err)

	got := pendingNudge(dir, now, 14*24*time.Hour)
	require.NotNil(t, got)

	after, err := os.ReadDir(filepath.Join(dir, "raw"))
	require.NoError(t, err)
	assert.Len(t, after, len(before), "the nudge must not promote or reject anything")
	assert.Contains(t, got.Hint, "brain_pending", "the nudge should say how to look, not act")
}

func TestPendingNudge_SurvivesAnUnreadableQueue(t *testing.T) {
	// brain_context is a hot path; a broken raw/ dir must degrade to silence
	// rather than failing the whole context call.
	dir := t.TempDir()
	require.NoError(t, os.WriteFile(filepath.Join(dir, "raw"), []byte("not a directory"), 0o644))

	assert.NotPanics(t, func() {
		assert.Nil(t, pendingNudge(dir, time.Now(), 14*24*time.Hour))
	})
}

func TestBrainContext_CarriesTheNudgeWithoutFailingWhenTheQueueIsEmpty(t *testing.T) {
	// The wiring, not the summary: a nudge that never reaches a caller is the
	// same as no nudge, and brain_context must still work with no queue.
	dir := t.TempDir()
	srv := NewServer(dir, nil, nil, nil)

	raw, err := srv.brainContext(context.Background(),
		json.RawMessage(`{"project_root":"/home/mathias/dev/AGENTS/hyperguild"}`))
	require.NoError(t, err)

	var empty map[string]any
	require.NoError(t, json.Unmarshal(raw, &empty))
	assert.NotContains(t, empty, "pending_review", "silence when nothing is aging")

	writePending(t, dir, "ancient.md", 200*24*time.Hour, time.Now())

	raw, err = srv.brainContext(context.Background(),
		json.RawMessage(`{"project_root":"/home/mathias/dev/AGENTS/hyperguild"}`))
	require.NoError(t, err)

	var withQueue map[string]any
	require.NoError(t, json.Unmarshal(raw, &withQueue))
	nudge, ok := withQueue["pending_review"].(map[string]any)
	require.True(t, ok, "the nudge must reach the caller: %v", withQueue)
	assert.Equal(t, float64(1), nudge["aging"])
	assert.Equal(t, "ancient.md", nudge["oldest"])
}