package worktree

import (
	"context"
	"errors"
	"expvar"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"testing"
	"time"

	"github.com/kandev/kandev/internal/common/subproc"
)

// hangOnRevParseScript is the shared fake-git script body used by the timeout
// regression tests. It sleeps indefinitely on `git rev-parse` and no-ops on
// everything else (including `fetch`), so branchExists, currentBranch, and
// the pullBaseBranch path that calls them all exercise the hang scenario.
const hangOnRevParseScript = `
case "${1:-}" in
  rev-parse)
    sleep 30
    exit 0
    ;;
  *)
    exit 0
    ;;
esac
`

const hangOnUpdateRefScript = `
case "${1:-}" in
  update-ref)
    sleep 30
    exit 0
    ;;
  *)
    exit 0
    ;;
esac
`

type boundedBranchMetadataStore struct{ mockStore }

func (s *boundedBranchMetadataStore) CountWorktreeBranchOwners(context.Context, string, string) (int, error) {
	return 1, nil
}

func (s *boundedBranchMetadataStore) PersistBranchRecoveryHead(context.Context, string, string, string) (bool, error) {
	return true, nil
}

func (s *boundedBranchMetadataStore) PersistBranchCompactionComplete(context.Context, string, string) (bool, error) {
	return true, nil
}

// TestBranchExists_RespectsContextDeadline verifies that branchExists cancels
// the underlying git subprocess when its caller-provided context expires.
func TestBranchExists_RespectsContextDeadline(t *testing.T) {
	scriptDir := writeFakeGitScript(t, hangOnRevParseScript)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	cfg := newTestConfig(t)
	mgr, err := NewManager(cfg, newMockStore(), newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
	defer cancel()

	start := time.Now()
	exists, err := mgr.branchExists(ctx, t.TempDir(), "main")
	elapsed := time.Since(start)

	if exists {
		t.Fatalf("branchExists() = true, want false on hanging git")
	}
	if err == nil {
		t.Fatalf("branchExists() err = nil, want non-nil on ctx cancellation")
	}
	if elapsed > 2*time.Second {
		t.Fatalf("branchExists() took %v, want <2s (ctx not propagated to subprocess)", elapsed)
	}
}

// TestCurrentBranch_RespectsContextDeadline verifies that currentBranch
// cancels the git subprocess when its caller-provided context expires.
func TestCurrentBranch_RespectsContextDeadline(t *testing.T) {
	scriptDir := writeFakeGitScript(t, hangOnRevParseScript)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	cfg := newTestConfig(t)
	mgr, err := NewManager(cfg, newMockStore(), newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), 200*time.Millisecond)
	defer cancel()

	start := time.Now()
	branch := mgr.currentBranch(ctx, t.TempDir())
	elapsed := time.Since(start)

	if branch != "" {
		t.Fatalf("currentBranch() = %q, want empty on hanging git", branch)
	}
	if elapsed > 2*time.Second {
		t.Fatalf("currentBranch() took %v, want <2s (ctx not propagated to subprocess)", elapsed)
	}
}

// TestBranchExists_BoundedWhenCallerHasNoDeadline pins the behaviour of the
// Manager's internal inspectTimeout. With a background (never-cancelled)
// caller ctx, branchExists must still return within m.inspectTimeout so a
// future refactor that drops the wrapping timeout cannot silently regress
// the fix. We shrink inspectTimeout for the test to keep it fast.
func TestBranchExists_BoundedWhenCallerHasNoDeadline(t *testing.T) {
	scriptDir := writeFakeGitScript(t, hangOnRevParseScript)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	cfg := newTestConfig(t)
	mgr, err := NewManager(cfg, newMockStore(), newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}
	mgr.inspectTimeout = 300 * time.Millisecond

	start := time.Now()
	exists, err := mgr.branchExists(context.Background(), t.TempDir(), "main")
	elapsed := time.Since(start)

	if exists {
		t.Fatalf("branchExists() = true, want false on hanging git")
	}
	if err == nil {
		t.Fatalf("branchExists() err = nil, want non-nil on inspectTimeout firing")
	}
	// Budget = inspectTimeout + WaitDelay for subprocess pipe cleanup + slack.
	if elapsed > 2*time.Second {
		t.Fatalf("branchExists() took %v, want <2s (inspectTimeout not applied)", elapsed)
	}
}

// TestResolveCommit_BoundedWhenCallerHasNoDeadline verifies that commit
// probes used by locked cleanup cannot leave a repository lock held by a
// stalled Git process.
func TestResolveCommit_BoundedWhenCallerHasNoDeadline(t *testing.T) {
	scriptDir := writeFakeGitScript(t, hangOnRevParseScript)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	mgr, err := NewManager(newTestConfig(t), newMockStore(), newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}
	mgr.inspectTimeout = 300 * time.Millisecond

	start := time.Now()
	commit, err := mgr.resolveCommit(context.Background(), t.TempDir(), "refs/heads/main")
	elapsed := time.Since(start)

	if commit != "" {
		t.Fatalf("resolveCommit() = %q, want empty on hanging git", commit)
	}
	if err == nil {
		t.Fatal("resolveCommit() err = nil, want timeout error")
	}
	if elapsed > 2*time.Second {
		t.Fatalf("resolveCommit() took %v, want <2s (inspect timeout not applied)", elapsed)
	}
}

func TestDeleteExpectedBranchRef_BoundedWhenUpdateRefHangs(t *testing.T) {
	scriptDir := writeFakeGitScript(t, hangOnUpdateRefScript)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	store := &boundedBranchMetadataStore{mockStore: *newMockStore()}
	mgr, err := NewManager(newTestConfig(t), store, newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}
	mgr.inspectTimeout = 300 * time.Millisecond

	wt := &Worktree{ID: "wt-timeout", RepositoryPath: t.TempDir(), Branch: "feature/timeout"}
	start := time.Now()
	reason := mgr.deleteExpectedBranchRef(context.Background(), store, wt, strings.Repeat("a", 40))
	elapsed := time.Since(start)

	if reason != RetainedSafeDeleteRefused {
		t.Fatalf("deleteExpectedBranchRef() reason = %q, want %q", reason, RetainedSafeDeleteRefused)
	}
	if elapsed > 2*time.Second {
		t.Fatalf("deleteExpectedBranchRef() took %v, want <2s", elapsed)
	}
}

func TestRestoreManagedBranchFromRecoveryHead_BoundsUpdateRefAdmissionAndReleasesRepoLock(t *testing.T) {
	restoreCap := setGitThrottleCapForTest(2)
	t.Cleanup(restoreCap)

	recoverySHA := strings.Repeat("a", 40)
	barrierDir := t.TempDir()
	revParseStarted := filepath.Join(barrierDir, "rev-parse-started")
	allowRevParse := filepath.Join(barrierDir, "allow-rev-parse")
	scriptDir := writeFakeGitScript(t, `
case "${1:-}" in
  rev-parse)
    : > "`+revParseStarted+`"
    while [ ! -f "`+allowRevParse+`" ]; do sleep 0.01; done
    printf '%s\n' "`+recoverySHA+`"
    ;;
  update-ref)
    exit 0
    ;;
  *)
    exit 0
    ;;
esac
`)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	mgr, err := NewManager(newTestConfig(t), newMockStore(), newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}
	mgr.inspectTimeout = 300 * time.Millisecond
	repoPath := t.TempDir()
	repoLock := mgr.getRepoLock(repoPath)
	firstHold, err := subproc.AcquireGit(context.Background(), subproc.GitLifecycle)
	if err != nil {
		t.Fatalf("hold first lifecycle slot: %v", err)
	}
	t.Cleanup(firstHold)

	resultCh := make(chan error, 1)
	go func() {
		repoLock.Lock()
		err := mgr.restoreManagedBranchFromRecoveryHeadLocked(context.Background(), &Worktree{
			RepositoryPath:  repoPath,
			Branch:          "feature/recovery-timeout",
			BranchOwner:     BranchOwnerManaged,
			RecoveryHeadSHA: recoverySHA,
		})
		repoLock.Unlock()
		resultCh <- err
	}()
	waitForFile(t, revParseStarted)

	secondHoldCh := make(chan func(), 1)
	secondHoldErrCh := make(chan error, 1)
	go func() {
		release, acquireErr := subproc.AcquireGit(context.Background(), subproc.GitLifecycle)
		if acquireErr != nil {
			secondHoldErrCh <- acquireErr
			return
		}
		secondHoldCh <- release
	}()
	waitForGitLifecycleWaiters(t, 1)
	if err := os.WriteFile(allowRevParse, []byte("go"), 0o600); err != nil {
		t.Fatalf("release rev-parse barrier: %v", err)
	}
	var secondHold func()
	select {
	case err := <-secondHoldErrCh:
		t.Fatalf("hold second lifecycle slot: %v", err)
	case secondHold = <-secondHoldCh:
	case <-time.After(time.Second):
		t.Fatal("second lifecycle slot was not acquired")
	}
	t.Cleanup(secondHold)

	select {
	case err := <-resultCh:
		if !errors.Is(err, context.DeadlineExceeded) {
			t.Fatalf("restore error = %v, want bounded update-ref admission deadline", err)
		}
	case <-time.After(2 * time.Second):
		t.Fatal("restore remained blocked on saturated update-ref admission")
	}
	if !repoLock.TryLock() {
		t.Fatal("repository lock remained held after bounded recovery restore")
	}
	repoLock.Unlock()
}

func waitForFile(t *testing.T, path string) {
	t.Helper()
	deadline := time.Now().Add(time.Second)
	for time.Now().Before(deadline) {
		if _, err := os.Stat(path); err == nil {
			return
		}
		time.Sleep(10 * time.Millisecond)
	}
	t.Fatalf("file %s was not created", path)
}

func waitForGitLifecycleWaiters(t *testing.T, want int64) {
	t.Helper()
	deadline := time.Now().Add(time.Second)
	for time.Now().Before(deadline) {
		if got := gitLifecycleWaiters(); got == want {
			return
		}
		time.Sleep(10 * time.Millisecond)
	}
	t.Fatalf("git lifecycle waiters did not reach %d (got %d)", want, gitLifecycleWaiters())
}

func gitLifecycleWaiters() int64 {
	vars, ok := expvar.Get("subproc_class_waiters").(*expvar.Map)
	if !ok {
		return 0
	}
	value := vars.Get("pool=git;class=lifecycle")
	if value == nil {
		return 0
	}
	got, _ := strconv.ParseInt(value.String(), 10, 64)
	return got
}

// TestCreate_HangingRevParseReleasesRepoLock is the core regression test for
// the reported symptom: a hung git rev-parse during Create must not keep the
// per-repo mutex locked indefinitely. Before the fix, branchExists and
// currentBranch ignored ctx, so a backend restart was the only way to clear
// the lock. After the fix, ctx cancellation propagates to the git subprocess
// and Create returns, releasing the lock for subsequent callers.
func TestCreate_HangingRevParseReleasesRepoLock(t *testing.T) {
	scriptDir := writeFakeGitScript(t, hangOnRevParseScript)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	cfg := newTestConfig(t)
	mgr, err := NewManager(cfg, newMockStore(), newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}
	mgr.fetchTimeout = 100 * time.Millisecond
	mgr.pullTimeout = 100 * time.Millisecond

	repoPath := t.TempDir()
	if err := os.MkdirAll(repoPath+"/.git", 0755); err != nil {
		t.Fatalf("failed to create .git dir: %v", err)
	}

	req := CreateRequest{
		TaskID:             "task-a",
		SessionID:          "sess-a",
		TaskTitle:          "hang repro",
		RepositoryPath:     repoPath,
		BaseBranch:         "main",
		PullBeforeWorktree: true,
		TaskDirName:        "task-a",
		RepoName:           "repo-a",
	}

	// Short caller deadline exercises ctx propagation through branchExists
	// and currentBranch. Before the fix these ignored ctx and slept the full
	// 30s in the fake git script, holding repoLock the entire time.
	ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
	defer cancel()

	start := time.Now()
	_, err = mgr.Create(ctx, req)
	elapsed := time.Since(start)
	if err == nil {
		t.Fatalf("Create() err = nil, want error on hanging git")
	}
	// Budget: inspect timeout + WaitDelay per subprocess kill, bounded by a
	// few subprocess kills and any lock bookkeeping. Pre-fix this was ~30s.
	if elapsed > 10*time.Second {
		t.Fatalf("Create() took %v, want <10s (lock held during hung git)", elapsed)
	}

	// Confirm the repo lock was released: a second Create call must be able
	// to acquire it without waiting. We use a fresh context so the call can
	// run briefly, then cancel; all we care about is that Lock() didn't
	// block us out.
	lockCtx, lockCancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
	defer lockCancel()

	lockStart := time.Now()
	done := make(chan struct{})
	go func() {
		defer close(done)
		_, _ = mgr.Create(lockCtx, req)
	}()
	select {
	case <-done:
	case <-time.After(10 * time.Second):
		t.Fatalf("second Create() stuck on repo lock (elapsed %v)", time.Since(lockStart))
	}
}

// TestCreate_InspectTimeoutDoesNotSurfaceAsInvalidBaseBranch pins the bug
// where a hung `git rev-parse --verify <base>` (e.g. a stalled NFS / SMB
// mount) caused branchExists to return false and Create to surface
// ErrInvalidBaseBranch — falsely claiming the base branch did not exist when
// in fact the check timed out. Callers must see the underlying timeout, not
// a misleading "branch not found" error that triggers task FAILED states.
func TestCreate_InspectTimeoutDoesNotSurfaceAsInvalidBaseBranch(t *testing.T) {
	scriptDir := writeFakeGitScript(t, hangOnRevParseScript)
	t.Setenv("PATH", scriptDir+string(os.PathListSeparator)+os.Getenv("PATH"))

	cfg := newTestConfig(t)
	mgr, err := NewManager(cfg, newMockStore(), newTestLogger())
	if err != nil {
		t.Fatalf("NewManager failed: %v", err)
	}
	// Tight inspect timeout so the test completes quickly.
	mgr.inspectTimeout = 200 * time.Millisecond

	repoPath := t.TempDir()
	if err := os.MkdirAll(repoPath+"/.git", 0755); err != nil {
		t.Fatalf("failed to create .git dir: %v", err)
	}

	req := CreateRequest{
		TaskID:         "task-a",
		SessionID:      "sess-a",
		TaskTitle:      "inspect timeout repro",
		RepositoryPath: repoPath,
		BaseBranch:     "master",
		TaskDirName:    "task-a",
		RepoName:       "repo-a",
	}

	_, err = mgr.Create(context.Background(), req)
	if err == nil {
		t.Fatalf("Create() err = nil, want timeout error on hanging git rev-parse")
	}
	if errors.Is(err, ErrInvalidBaseBranch) {
		t.Fatalf("Create() err = %v, must NOT be ErrInvalidBaseBranch on inspect timeout (regression: misleading 'base branch does not exist' surfaced to users)", err)
	}
}