package cache

import (
	"bytes"
	"context"
	"io"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"codeberg.org/VARASYS/ZDDC/zddc/internal/config"
)

func newOutboxFixture(t *testing.T, upstreamHandler http.HandlerFunc) (*Cache, *Outbox, *httptest.Server) {
	t.Helper()
	upstream := httptest.NewServer(upstreamHandler)
	t.Cleanup(upstream.Close)
	root := t.TempDir()
	c, err := New(config.Config{Root: root, Upstream: upstream.URL, Mode: "cache"})
	if err != nil {
		t.Fatalf("New: %v", err)
	}
	o, err := NewOutbox(c)
	if err != nil {
		t.Fatalf("NewOutbox: %v", err)
	}
	c.SetOutbox(o)
	return c, o, upstream
}

func TestNewOutbox_CreatesDirectoryWith0700(t *testing.T) {
	root := t.TempDir()
	c, _ := New(config.Config{Root: root, Upstream: "http://example.com", Mode: "cache"})
	o, err := NewOutbox(c)
	if err != nil {
		t.Fatalf("NewOutbox: %v", err)
	}
	want := filepath.Join(root, OutboxDir)
	if o.Dir() != want {
		t.Errorf("Dir() = %q, want %q", o.Dir(), want)
	}
	info, err := os.Stat(want)
	if err != nil {
		t.Fatalf("stat: %v", err)
	}
	if mode := info.Mode().Perm(); mode&0o077 != 0 {
		t.Errorf("dir mode %o exposes group/other bits", mode)
	}
}

func TestEnqueue_PersistsBodyAndMeta(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {})
	body := []byte("hello world")
	r := httptest.NewRequest(http.MethodPut, "/foo.txt", bytes.NewReader(body))
	r.Header.Set("Content-Type", "text/plain")
	base := time.Date(2026, 5, 8, 12, 0, 0, 0, time.UTC)

	entry, err := o.Enqueue(r, base)
	if err != nil {
		t.Fatalf("Enqueue: %v", err)
	}
	if entry.ID == "" {
		t.Fatal("entry.ID empty")
	}
	if entry.Method != "PUT" || entry.RawURI != "/foo.txt" {
		t.Errorf("entry method/uri wrong: %+v", entry)
	}
	if entry.ContentType != "text/plain" {
		t.Errorf("ContentType = %q", entry.ContentType)
	}
	if !entry.BaseModTime.Equal(base) {
		t.Errorf("BaseModTime = %v, want %v", entry.BaseModTime, base)
	}

	// Body file should contain the request bytes.
	got, err := os.ReadFile(filepath.Join(o.Dir(), entry.ID, "body.bin"))
	if err != nil {
		t.Fatalf("read body.bin: %v", err)
	}
	if !bytes.Equal(got, body) {
		t.Errorf("body = %q, want %q", got, body)
	}
}

func TestPending_OrdersByID(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {})
	for i := 0; i < 3; i++ {
		r := httptest.NewRequest(http.MethodPut, "/x.txt", strings.NewReader("data"))
		_, err := o.Enqueue(r, time.Time{})
		if err != nil {
			t.Fatalf("enqueue %d: %v", i, err)
		}
		time.Sleep(2 * time.Millisecond) // ensure unique unix-nano IDs
	}
	got, err := o.Pending()
	if err != nil {
		t.Fatalf("Pending: %v", err)
	}
	if len(got) != 3 {
		t.Fatalf("len = %d", len(got))
	}
	for i := 1; i < len(got); i++ {
		if got[i].ID < got[i-1].ID {
			t.Errorf("entries not lex-sorted at index %d: %q < %q", i, got[i].ID, got[i-1].ID)
		}
	}
}

func TestReplay_DeletesOnSuccess(t *testing.T) {
	var lastBody []byte
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		lastBody, _ = io.ReadAll(r.Body)
		w.WriteHeader(http.StatusNoContent)
	})
	r := httptest.NewRequest(http.MethodPut, "/foo.txt", bytes.NewReader([]byte("payload")))
	r.Header.Set("Content-Type", "text/plain")
	entry, _ := o.Enqueue(r, time.Time{})

	replayed, conflicts, err := o.Replay(context.Background())
	if err != nil {
		t.Fatalf("Replay: %v", err)
	}
	if replayed != 1 || conflicts != 0 {
		t.Errorf("replayed=%d conflicts=%d, want 1/0", replayed, conflicts)
	}
	if string(lastBody) != "payload" {
		t.Errorf("upstream got body %q", lastBody)
	}
	// Entry directory should be gone.
	if _, err := os.Stat(filepath.Join(o.Dir(), entry.ID)); !os.IsNotExist(err) {
		t.Errorf("entry not removed: %v", err)
	}
}

func TestReplay_412RenamesToConflict(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusPreconditionFailed)
	})
	r := httptest.NewRequest(http.MethodPut, "/foo.txt", bytes.NewReader([]byte("x")))
	entry, _ := o.Enqueue(r, time.Date(2026, 5, 1, 0, 0, 0, 0, time.UTC))

	replayed, conflicts, _ := o.Replay(context.Background())
	if replayed != 0 || conflicts != 1 {
		t.Errorf("replayed=%d conflicts=%d, want 0/1", replayed, conflicts)
	}
	// Original entry dir gone, conflict-renamed dir present.
	if _, err := os.Stat(filepath.Join(o.Dir(), entry.ID)); !os.IsNotExist(err) {
		t.Error("original entry not renamed")
	}
	entries, _ := os.ReadDir(o.Dir())
	foundConflict := false
	for _, e := range entries {
		if strings.HasPrefix(e.Name(), entry.ID+outboxConflictPrefix) {
			foundConflict = true
		}
	}
	if !foundConflict {
		t.Errorf("no conflict-renamed dir found among %v", dirNames(entries))
	}
	// Pending should now exclude the conflict.
	pending, _ := o.Pending()
	if len(pending) != 0 {
		t.Errorf("Pending() includes conflicts: %d entries", len(pending))
	}
}

func TestReplay_NetworkErrorLeavesEntry(t *testing.T) {
	root := t.TempDir()
	c, _ := New(config.Config{Root: root, Upstream: "http://127.0.0.1:1", Mode: "cache"})
	c.client.Timeout = 200 * time.Millisecond
	o, _ := NewOutbox(c)
	r := httptest.NewRequest(http.MethodPut, "/foo.txt", bytes.NewReader([]byte("retry-me")))
	entry, _ := o.Enqueue(r, time.Time{})

	replayed, conflicts, _ := o.Replay(context.Background())
	if replayed != 0 || conflicts != 0 {
		t.Errorf("replayed=%d conflicts=%d, want 0/0 (deferred)", replayed, conflicts)
	}
	if _, err := os.Stat(filepath.Join(o.Dir(), entry.ID)); err != nil {
		t.Errorf("entry was removed despite network error: %v", err)
	}
}

func TestReplay_4xxNon412Drops(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		http.Error(w, "Forbidden", http.StatusForbidden)
	})
	r := httptest.NewRequest(http.MethodPut, "/foo.txt", bytes.NewReader([]byte("x")))
	entry, _ := o.Enqueue(r, time.Time{})

	replayed, conflicts, _ := o.Replay(context.Background())
	// 4xx-other-than-412 counts as "done" (we drop it; retrying won't help).
	if replayed != 1 || conflicts != 0 {
		t.Errorf("replayed=%d conflicts=%d", replayed, conflicts)
	}
	if _, err := os.Stat(filepath.Join(o.Dir(), entry.ID)); !os.IsNotExist(err) {
		t.Errorf("entry not dropped after 403: %v", err)
	}
}

func TestReplay_5xxLeavesEntry(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		http.Error(w, "Internal", http.StatusInternalServerError)
	})
	r := httptest.NewRequest(http.MethodPut, "/foo.txt", bytes.NewReader([]byte("x")))
	entry, _ := o.Enqueue(r, time.Time{})

	replayed, conflicts, _ := o.Replay(context.Background())
	if replayed != 0 || conflicts != 0 {
		t.Errorf("replayed=%d conflicts=%d, want 0/0 (deferred)", replayed, conflicts)
	}
	if _, err := os.Stat(filepath.Join(o.Dir(), entry.ID)); err != nil {
		t.Errorf("entry should remain after 500: %v", err)
	}
}

func TestReplay_SendsIfUnmodifiedSinceWhenBaseSet(t *testing.T) {
	var seenIUS string
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		seenIUS = r.Header.Get("If-Unmodified-Since")
		w.WriteHeader(http.StatusNoContent)
	})
	base := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
	r := httptest.NewRequest(http.MethodPut, "/foo.txt", bytes.NewReader([]byte("x")))
	_, _ = o.Enqueue(r, base)

	_, _, _ = o.Replay(context.Background())
	if seenIUS == "" {
		t.Error("upstream did not see If-Unmodified-Since")
	}
	parsed, err := http.ParseTime(seenIUS)
	if err != nil {
		t.Fatalf("parse IUS: %v", err)
	}
	if !parsed.Equal(base) {
		t.Errorf("IUS = %v, want %v", parsed, base)
	}
}

func TestReplay_OmitsIfUnmodifiedSinceForPOST(t *testing.T) {
	var seenIUS string
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		seenIUS = r.Header.Get("If-Unmodified-Since")
		w.WriteHeader(http.StatusOK)
	})
	r := httptest.NewRequest(http.MethodPost, "/submit", bytes.NewReader([]byte("data")))
	_, _ = o.Enqueue(r, time.Time{})

	_, _, _ = o.Replay(context.Background())
	if seenIUS != "" {
		t.Errorf("POST should not send If-Unmodified-Since, got %q", seenIUS)
	}
}

func TestReplay_PreservesQueryString(t *testing.T) {
	var seenURI string
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		seenURI = r.URL.RequestURI()
		w.WriteHeader(http.StatusOK)
	})
	r := httptest.NewRequest(http.MethodPost, "/foo?x=1&y=2", strings.NewReader(""))
	_, _ = o.Enqueue(r, time.Time{})
	_, _, _ = o.Replay(context.Background())
	if seenURI != "/foo?x=1&y=2" {
		t.Errorf("upstream saw URI %q", seenURI)
	}
}

func TestServeHTTP_OnlineWriteForwards(t *testing.T) {
	var lastBody []byte
	c, _, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		lastBody, _ = io.ReadAll(r.Body)
		w.WriteHeader(http.StatusCreated)
	})
	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodPut, "/x.txt", bytes.NewReader([]byte("data")))
	r.Header.Set("Content-Type", "text/plain")
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusCreated {
		t.Errorf("status = %d, want 201", rec.Code)
	}
	if string(lastBody) != "data" {
		t.Errorf("upstream body = %q", lastBody)
	}
	// No outbox entry should have been created for an online write.
	pending, _ := c.outbox.Pending()
	if len(pending) != 0 {
		t.Errorf("pending = %d, want 0", len(pending))
	}
}

func TestServeHTTP_OfflineWriteQueues(t *testing.T) {
	root := t.TempDir()
	c, _ := New(config.Config{Root: root, Upstream: "http://127.0.0.1:1", Mode: "cache"})
	c.client.Timeout = 200 * time.Millisecond
	o, _ := NewOutbox(c)
	c.SetOutbox(o)

	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodPut, "/x.txt", bytes.NewReader([]byte("offline-data")))
	r.Header.Set("Content-Type", "text/plain")
	c.ServeHTTP(rec, r)

	if rec.Code != http.StatusAccepted {
		t.Fatalf("status = %d, want 202; body=%q", rec.Code, rec.Body.String())
	}
	if got := rec.Header().Get(HeaderName); got != "queued" {
		t.Errorf("cache header = %q", got)
	}
	if !strings.Contains(rec.Body.String(), "outbox_id") {
		t.Errorf("body missing outbox_id: %q", rec.Body.String())
	}
	pending, _ := o.Pending()
	if len(pending) != 1 {
		t.Errorf("pending = %d, want 1", len(pending))
	}
}

func TestServeHTTP_OfflineWriteNoOutbox503(t *testing.T) {
	root := t.TempDir()
	c, _ := New(config.Config{Root: root, Upstream: "http://127.0.0.1:1", Mode: "cache"})
	c.client.Timeout = 200 * time.Millisecond
	// No outbox installed.

	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodPut, "/x.txt", bytes.NewReader([]byte("data")))
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusServiceUnavailable {
		t.Errorf("status = %d, want 503", rec.Code)
	}
}

func TestServeHTTP_OnlinePutEvictsCachedEntry(t *testing.T) {
	c, _, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusNoContent)
	})
	cached := filepath.Join(c.root, "x.txt")
	if err := os.WriteFile(cached, []byte("old"), 0o644); err != nil {
		t.Fatalf("seed: %v", err)
	}
	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodPut, "/x.txt", bytes.NewReader([]byte("new")))
	c.ServeHTTP(rec, r)
	if rec.Code != http.StatusNoContent {
		t.Fatalf("status = %d", rec.Code)
	}
	if _, err := os.Stat(cached); !os.IsNotExist(err) {
		t.Error("cached entry not evicted after successful PUT")
	}
}

func TestServeHTTP_PUTSendsIfUnmodifiedSinceFromCachedMtime(t *testing.T) {
	var seenIUS string
	c, _, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		seenIUS = r.Header.Get("If-Unmodified-Since")
		w.WriteHeader(http.StatusNoContent)
	})
	// Seed cached file with a specific mtime.
	cached := filepath.Join(c.root, "y.txt")
	if err := os.WriteFile(cached, []byte("old"), 0o644); err != nil {
		t.Fatalf("seed: %v", err)
	}
	when := time.Date(2026, 1, 1, 0, 0, 0, 0, time.UTC)
	if err := os.Chtimes(cached, when, when); err != nil {
		t.Fatalf("chtimes: %v", err)
	}

	rec := httptest.NewRecorder()
	r := httptest.NewRequest(http.MethodPut, "/y.txt", bytes.NewReader([]byte("new")))
	c.ServeHTTP(rec, r)
	if seenIUS == "" {
		t.Fatal("upstream did not see If-Unmodified-Since")
	}
	parsed, _ := http.ParseTime(seenIUS)
	if !parsed.Equal(when) {
		t.Errorf("IUS = %v, want %v (cached mtime)", parsed, when)
	}
}

func TestEnqueue_RejectsOversizeBody(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {})
	huge := make([]byte, MaxOutboxBodyBytes+10)
	r := httptest.NewRequest(http.MethodPut, "/big", bytes.NewReader(huge))
	_, err := o.Enqueue(r, time.Time{})
	if err == nil {
		t.Error("expected error for oversize body")
	}
}

func TestNewOutboxID_LexSortable(t *testing.T) {
	var ids []string
	for i := 0; i < 5; i++ {
		id, err := newOutboxID()
		if err != nil {
			t.Fatalf("id: %v", err)
		}
		ids = append(ids, id)
		time.Sleep(2 * time.Millisecond)
	}
	for i := 1; i < len(ids); i++ {
		if ids[i] <= ids[i-1] {
			t.Errorf("IDs not strictly increasing: %q vs %q", ids[i-1], ids[i])
		}
	}
}

func TestRunReplayLoop_StopsOnContextCancel(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	})
	ctx, cancel := context.WithCancel(context.Background())
	done := make(chan struct{})
	go func() {
		o.RunReplayLoop(ctx)
		close(done)
	}()
	cancel()
	select {
	case <-done:
		// ok
	case <-time.After(2 * time.Second):
		t.Fatal("RunReplayLoop did not exit on context cancel")
	}
}

func TestConcurrentEnqueue_NoIDCollision(t *testing.T) {
	_, o, _ := newOutboxFixture(t, func(w http.ResponseWriter, r *http.Request) {})
	const N = 30
	var wg sync.WaitGroup
	var fails int32
	for i := 0; i < N; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			r := httptest.NewRequest(http.MethodPut, "/x", strings.NewReader("data"))
			if _, err := o.Enqueue(r, time.Time{}); err != nil {
				atomic.AddInt32(&fails, 1)
			}
		}()
	}
	wg.Wait()
	if fails != 0 {
		t.Errorf("%d enqueues failed", fails)
	}
	pending, _ := o.Pending()
	if len(pending) != N {
		t.Errorf("pending = %d, want %d", len(pending), N)
	}
}

func dirNames(entries []os.DirEntry) []string {
	out := make([]string, len(entries))
	for i, e := range entries {
		out[i] = e.Name()
	}
	return out
}