package main

import (
	"context"
	"sync"
	"testing"
	"time"
)

// TestConcurrentComments_AllRetained — 100 goroutines add comments to the
// same post. All should land, no path collisions, no lost writes.
func TestConcurrentComments_AllRetained(t *testing.T) {
	s, _, _ := newTestStore(t)
	cp := &CreatePost{AuthorID: "scott", Body: "race test"}
	must(t, Submit(context.Background(), s, cp))

	const N = 100
	var wg sync.WaitGroup
	errCh := make(chan error, N)
	for i := 0; i < N; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			m := &AddComment{PostID: cp.ResolvedPostID(), AuthorID: "hermes", Body: "concurrent"}
			errCh <- Submit(context.Background(), s, m)
		}()
	}
	wg.Wait()
	close(errCh)
	for err := range errCh {
		if err != nil {
			t.Fatalf("concurrent submit: %v", err)
		}
	}
	comments := s.ListComments(cp.ResolvedPostID())
	if len(comments) != N {
		t.Fatalf("expected %d comments, got %d", N, len(comments))
	}
	// All paths must be unique and parseable.
	seen := make(map[string]bool, N)
	for _, c := range comments {
		if seen[c.Path] {
			t.Fatalf("duplicate path: %s", c.Path)
		}
		seen[c.Path] = true
	}
}

// TestBumpOrder_AfterConcurrentComments — concurrent comments land in some
// order, but the final post bump_at should be the time of the LAST comment.
// With the per-author coarse lock, mutations serialize, so the order is
// deterministic given the goroutine schedule. We don't assert exact order
// (that would be flaky); we assert that the final bump_at is the latest.
func TestBumpOrder_AfterConcurrentComments(t *testing.T) {
	s, clock, _ := newTestStore(t)
	cp := &CreatePost{AuthorID: "scott", Body: "bump order"}
	must(t, Submit(context.Background(), s, cp))
	initialBump := s.posts[cp.ResolvedPostID()].BumpedAt

	const N = 10
	var wg sync.WaitGroup
	for i := 0; i < N; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			clock.Advance(time.Second)
			m := &AddComment{PostID: cp.ResolvedPostID(), AuthorID: "hermes", Body: "x"}
			_ = Submit(context.Background(), s, m)
		}()
	}
	wg.Wait()

	got, _ := s.GetPost(cp.ResolvedPostID())
	if !got.BumpedAt.After(initialBump) {
		t.Fatalf("post should have been bumped past %v, got %v", initialBump, got.BumpedAt)
	}
}