package daemon

import (
	"context"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"banger/internal/api"
	"banger/internal/daemon/workspace"
	"banger/internal/model"
)

// exportGuestClient is a scriptable fake for RunScriptOutput used in export tests.
// Each call to RunScriptOutput returns the next response from the queue.
type exportGuestClient struct {
	responses []exportGuestResponse
	scripts   []string
	callIndex int
}

type exportGuestResponse struct {
	output []byte
	err    error
}

func (e *exportGuestClient) Close() error { return nil }

func (e *exportGuestClient) RunScript(_ context.Context, _ string, _ io.Writer) error {
	return nil
}

func (e *exportGuestClient) RunScriptOutput(_ context.Context, script string) ([]byte, error) {
	e.scripts = append(e.scripts, script)
	if e.callIndex >= len(e.responses) {
		return nil, nil
	}
	r := e.responses[e.callIndex]
	e.callIndex++
	return r.output, r.err
}

func (e *exportGuestClient) UploadFile(_ context.Context, _ string, _ os.FileMode, _ []byte, _ io.Writer) error {
	return nil
}

func (e *exportGuestClient) StreamTar(_ context.Context, _ string, _ string, _ io.Writer) error {
	return nil
}

func (e *exportGuestClient) StreamTarEntries(_ context.Context, _ string, _ []string, _ string, _ io.Writer) error {
	return nil
}

func newExportTestDaemonStore(t *testing.T, fake *exportGuestClient) *Daemon {
	t.Helper()
	db := openDaemonStore(t)
	d := &Daemon{
		store:  db,
		config: model.DaemonConfig{SSHKeyPath: filepath.Join(t.TempDir(), "id_ed25519")},
		logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
	}
	d.guestDial = func(_ context.Context, _ string, _ string) (guestSSHClient, error) {
		return fake, nil
	}
	return d
}

func TestExportVMWorkspace_HappyPath(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("exportbox", "image-export", "172.16.0.100")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	patch := []byte("diff --git a/file.go b/file.go\nindex 0000000..1111111 100644\n")
	names := []byte("file.go\n")

	fake := &exportGuestClient{
		responses: []exportGuestResponse{
			{output: patch},
			{output: names},
		},
	}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	result, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{
		IDOrName:  vm.Name,
		GuestPath: "/root/repo",
	})
	if err != nil {
		t.Fatalf("ExportVMWorkspace: %v", err)
	}
	if !result.HasChanges {
		t.Fatal("HasChanges = false, want true")
	}
	if string(result.Patch) != string(patch) {
		t.Fatalf("Patch = %q, want %q", result.Patch, patch)
	}
	if result.GuestPath != "/root/repo" {
		t.Fatalf("GuestPath = %q, want /root/repo", result.GuestPath)
	}
	if len(result.ChangedFiles) != 1 || result.ChangedFiles[0] != "file.go" {
		t.Fatalf("ChangedFiles = %v, want [file.go]", result.ChangedFiles)
	}
	if fake.callIndex != 2 {
		t.Fatalf("RunScriptOutput call count = %d, want 2", fake.callIndex)
	}
	// No base_commit provided: diff ref must be HEAD.
	for _, script := range fake.scripts {
		if !strings.Contains(script, "HEAD") {
			t.Fatalf("script missing HEAD ref: %q", script)
		}
	}
	if result.BaseCommit != "HEAD" {
		t.Fatalf("BaseCommit = %q, want HEAD", result.BaseCommit)
	}
}

func TestExportVMWorkspace_WithBaseCommit(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("exportbox-base", "image-export", "172.16.0.105")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	// Simulate: worker committed inside the VM. Without base_commit the diff
	// against the new HEAD would be empty. With base_commit we capture
	// everything since the original checkout.
	patch := []byte("diff --git a/worker.go b/worker.go\nindex 0000000..abcdef 100644\n")
	names := []byte("worker.go\n")

	fake := &exportGuestClient{
		responses: []exportGuestResponse{
			{output: patch},
			{output: names},
		},
	}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	const prepareCommit = "abc1234deadbeef"
	result, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{
		IDOrName:   vm.Name,
		BaseCommit: prepareCommit,
	})
	if err != nil {
		t.Fatalf("ExportVMWorkspace: %v", err)
	}
	if !result.HasChanges {
		t.Fatal("HasChanges = false, want true")
	}
	if result.BaseCommit != prepareCommit {
		t.Fatalf("BaseCommit = %q, want %q", result.BaseCommit, prepareCommit)
	}
	// Both scripts must reference the caller-supplied commit, not HEAD.
	for _, script := range fake.scripts {
		if strings.Contains(script, " HEAD") {
			t.Fatalf("script used HEAD instead of base_commit: %q", script)
		}
		if !strings.Contains(script, prepareCommit) {
			t.Fatalf("script missing base_commit %q: %q", prepareCommit, script)
		}
	}
}

func TestExportVMWorkspace_BaseCommitFallsBackToHEAD(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("exportbox-nobase", "image-export", "172.16.0.106")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	fake := &exportGuestClient{
		responses: []exportGuestResponse{
			{output: nil},
			{output: nil},
		},
	}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	result, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{
		IDOrName:   vm.Name,
		BaseCommit: "", // omitted
	})
	if err != nil {
		t.Fatalf("ExportVMWorkspace: %v", err)
	}
	if result.BaseCommit != "HEAD" {
		t.Fatalf("BaseCommit = %q, want HEAD when not supplied", result.BaseCommit)
	}
	for _, script := range fake.scripts {
		if !strings.Contains(script, "HEAD") {
			t.Fatalf("script missing HEAD fallback: %q", script)
		}
	}
}

func TestExportVMWorkspace_NoChanges(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("exportbox-empty", "image-export", "172.16.0.101")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	// Both scripts return empty output (no changes).
	fake := &exportGuestClient{
		responses: []exportGuestResponse{
			{output: nil},
			{output: nil},
		},
	}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	result, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{
		IDOrName: vm.Name,
	})
	if err != nil {
		t.Fatalf("ExportVMWorkspace: %v", err)
	}
	if result.HasChanges {
		t.Fatal("HasChanges = true, want false")
	}
	if len(result.Patch) != 0 {
		t.Fatalf("Patch = %q, want empty", result.Patch)
	}
	if len(result.ChangedFiles) != 0 {
		t.Fatalf("ChangedFiles = %v, want empty", result.ChangedFiles)
	}
}

func TestExportVMWorkspace_DefaultGuestPath(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("exportbox-default", "image-export", "172.16.0.102")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	fake := &exportGuestClient{
		responses: []exportGuestResponse{
			{output: nil},
			{output: nil},
		},
	}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	// GuestPath omitted — should default to /root/repo.
	result, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{
		IDOrName: vm.Name,
	})
	if err != nil {
		t.Fatalf("ExportVMWorkspace: %v", err)
	}
	if result.GuestPath != "/root/repo" {
		t.Fatalf("GuestPath = %q, want /root/repo", result.GuestPath)
	}
}

func TestExportVMWorkspace_VMNotRunning(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	vm := testVM("exportbox-stopped", "image-export", "172.16.0.103")
	vm.State = model.VMStateStopped

	fake := &exportGuestClient{}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	// VM is stopped — no handle seed; vmAlive must return false.

	_, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{
		IDOrName: vm.Name,
	})
	if err == nil || !strings.Contains(err.Error(), "not running") {
		t.Fatalf("error = %v, want 'not running' error", err)
	}
	if fake.callIndex != 0 {
		t.Fatal("RunScriptOutput should not be called when VM is not running")
	}
}

func TestExportVMWorkspace_MultipleChangedFiles(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("exportbox-multi", "image-export", "172.16.0.104")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	patch := []byte("diff --git a/a.go b/a.go\n--- a/a.go\n+++ b/a.go\n")
	names := []byte("a.go\nb.go\nnew/file.go\n")

	fake := &exportGuestClient{
		responses: []exportGuestResponse{
			{output: patch},
			{output: names},
		},
	}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	result, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{
		IDOrName: vm.Name,
	})
	if err != nil {
		t.Fatalf("ExportVMWorkspace: %v", err)
	}
	if len(result.ChangedFiles) != 3 {
		t.Fatalf("ChangedFiles = %v, want 3 entries", result.ChangedFiles)
	}
	want := []string{"a.go", "b.go", "new/file.go"}
	for i, f := range want {
		if result.ChangedFiles[i] != f {
			t.Fatalf("ChangedFiles[%d] = %q, want %q", i, result.ChangedFiles[i], f)
		}
	}
}

// TestPrepareVMWorkspace_ReleasesVMLockDuringGuestIO is a regression
// guard for an earlier design that held the per-VM mutex across SSH
// dial, tar streaming, and remote chmod. A long import could then
// block unrelated lifecycle ops (vm stop / delete / restart) on the
// same VM until it completed. The fix switched to a dedicated
// workspaceLocks set for I/O, with vmLocks held only for the brief
// state-validation phase. This test kicks off a prepare that blocks
// inside the import step and then asserts the VM mutex is acquirable
// while the prepare is mid-flight.
func TestPrepareVMWorkspace_ReleasesVMLockDuringGuestIO(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("lockbox", "image-x", "172.16.0.210")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	d := &Daemon{
		store:  openDaemonStore(t),
		config: model.DaemonConfig{SSHKeyPath: filepath.Join(t.TempDir(), "id_ed25519")},
		logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
	}
	d.guestWaitForSSH = func(_ context.Context, _, _ string, _ time.Duration) error { return nil }
	d.guestDial = func(_ context.Context, _, _ string) (guestSSHClient, error) {
		return &exportGuestClient{}, nil
	}
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	// Install the workspace seams on this daemon instance. InspectRepo
	// returns a trivial spec so the real filesystem isn't touched;
	// Import blocks until we say go.
	importStarted := make(chan struct{})
	releaseImport := make(chan struct{})
	d.workspaceInspectRepo = func(context.Context, string, string, string) (workspace.RepoSpec, error) {
		return workspace.RepoSpec{RepoName: "fake", RepoRoot: "/tmp/fake"}, nil
	}
	d.workspaceImport = func(context.Context, workspace.GuestClient, workspace.RepoSpec, string, model.WorkspacePrepareMode) error {
		close(importStarted)
		<-releaseImport
		return nil
	}

	// Kick off prepare in a goroutine. It will block inside the import.
	prepareDone := make(chan error, 1)
	go func() {
		_, err := d.PrepareVMWorkspace(ctx, api.VMWorkspacePrepareParams{
			IDOrName:   vm.Name,
			SourcePath: "/tmp/fake",
		})
		prepareDone <- err
	}()

	// Wait for prepare to reach the guest-I/O phase (past the VM
	// mutex) before testing the assertion.
	select {
	case <-importStarted:
	case <-time.After(2 * time.Second):
		t.Fatal("import never started; prepare blocked before reaching guest I/O")
	}

	// With the fix in place, the VM mutex is free even though the
	// import is in flight. Acquiring it must not wait.
	acquired := make(chan struct{})
	go func() {
		unlock := d.lockVMID(vm.ID)
		close(acquired)
		unlock()
	}()
	select {
	case <-acquired:
	case <-time.After(500 * time.Millisecond):
		close(releaseImport) // unblock the goroutine so the test can exit
		<-prepareDone
		t.Fatal("VM mutex held during guest I/O — lifecycle ops would block behind workspace prepare")
	}

	// Now let the import finish and make sure prepare returns.
	close(releaseImport)
	select {
	case err := <-prepareDone:
		if err != nil {
			t.Fatalf("prepare returned error: %v", err)
		}
	case <-time.After(2 * time.Second):
		t.Fatal("prepare did not return after import unblocked")
	}
}

// TestPrepareVMWorkspace_SerialisesConcurrentPreparesOnSameVM asserts
// the workspaceLocks scope: two concurrent prepares on the same VM do
// NOT interleave, even though they no longer take the core VM mutex.
func TestPrepareVMWorkspace_SerialisesConcurrentPreparesOnSameVM(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("serialbox", "image-x", "172.16.0.211")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	d := &Daemon{
		store:  openDaemonStore(t),
		config: model.DaemonConfig{SSHKeyPath: filepath.Join(t.TempDir(), "id_ed25519")},
		logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
	}
	d.guestWaitForSSH = func(_ context.Context, _, _ string, _ time.Duration) error { return nil }
	d.guestDial = func(_ context.Context, _, _ string) (guestSSHClient, error) {
		return &exportGuestClient{}, nil
	}
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	d.workspaceInspectRepo = func(context.Context, string, string, string) (workspace.RepoSpec, error) {
		return workspace.RepoSpec{RepoName: "fake", RepoRoot: "/tmp/fake"}, nil
	}

	// Counter of simultaneous Import calls. Should never exceed 1.
	var active int32
	var maxObserved int32
	release := make(chan struct{})
	d.workspaceImport = func(context.Context, workspace.GuestClient, workspace.RepoSpec, string, model.WorkspacePrepareMode) error {
		n := atomic.AddInt32(&active, 1)
		for {
			prev := atomic.LoadInt32(&maxObserved)
			if n <= prev || atomic.CompareAndSwapInt32(&maxObserved, prev, n) {
				break
			}
		}
		<-release
		atomic.AddInt32(&active, -1)
		return nil
	}

	const n = 3
	done := make(chan error, n)
	for i := 0; i < n; i++ {
		go func() {
			_, err := d.PrepareVMWorkspace(ctx, api.VMWorkspacePrepareParams{
				IDOrName:   vm.Name,
				SourcePath: "/tmp/fake",
			})
			done <- err
		}()
	}

	// Give goroutines a moment to queue up.
	time.Sleep(100 * time.Millisecond)

	if got := atomic.LoadInt32(&active); got != 1 {
		close(release) // unblock to avoid hang
		for i := 0; i < n; i++ {
			<-done
		}
		t.Fatalf("%d concurrent imports, want exactly 1 (workspace lock should serialise)", got)
	}

	// Drain: release imports one at a time.
	for i := 0; i < n; i++ {
		release <- struct{}{}
	}
	close(release)
	for i := 0; i < n; i++ {
		if err := <-done; err != nil {
			t.Errorf("prepare #%d error: %v", i, err)
		}
	}
	if got := atomic.LoadInt32(&maxObserved); got != 1 {
		t.Fatalf("peak concurrent imports = %d, want 1", got)
	}
}

// TestExportVMWorkspace_DoesNotMutateRealIndex is a regression guard
// for an earlier design where `git add -A` ran against the guest's
// real `.git/index`, leaving staged changes behind after what the user
// thought was a read-only observation. Every export script must now
// route `git add -A` through a throwaway index selected by
// GIT_INDEX_FILE, and every script must clean that file up.
func TestExportVMWorkspace_DoesNotMutateRealIndex(t *testing.T) {
	t.Parallel()
	ctx := context.Background()

	apiSock := filepath.Join(t.TempDir(), "fc.sock")
	firecracker := startFakeFirecracker(t, apiSock)

	vm := testVM("exportbox-readonly", "image-export", "172.16.0.107")
	vm.State = model.VMStateRunning
	vm.Runtime.State = model.VMStateRunning
	vm.Runtime.APISockPath = apiSock

	fake := &exportGuestClient{
		responses: []exportGuestResponse{
			{output: []byte("diff --git a/x b/x\n")},
			{output: []byte("x\n")},
		},
	}
	d := newExportTestDaemonStore(t, fake)
	upsertDaemonVM(t, ctx, d.store, vm)
	d.setVMHandlesInMemory(vm.ID, model.VMHandles{PID: firecracker.Process.Pid})

	if _, err := d.ExportVMWorkspace(ctx, api.WorkspaceExportParams{IDOrName: vm.Name}); err != nil {
		t.Fatalf("ExportVMWorkspace: %v", err)
	}

	if len(fake.scripts) == 0 {
		t.Fatal("expected at least one export script to be sent")
	}
	for i, script := range fake.scripts {
		if !strings.Contains(script, "GIT_INDEX_FILE") {
			t.Errorf("script[%d] missing GIT_INDEX_FILE routing:\n%s", i, script)
		}
		// git add -A must ONLY appear on a line that also sets
		// GIT_INDEX_FILE. A bare occurrence would mutate the real
		// index.
		for _, line := range strings.Split(script, "\n") {
			if strings.Contains(line, "git add -A") && !strings.Contains(line, "GIT_INDEX_FILE") {
				t.Errorf("script[%d] has unscoped `git add -A`:\n%s", i, script)
				break
			}
		}
		if !strings.Contains(script, "git read-tree") {
			t.Errorf("script[%d] missing git read-tree (temp index seed):\n%s", i, script)
		}
		if !strings.Contains(script, "mktemp") {
			t.Errorf("script[%d] missing mktemp for temp index:\n%s", i, script)
		}
		if !strings.Contains(script, "trap") || !strings.Contains(script, "rm") {
			t.Errorf("script[%d] missing temp-index cleanup trap:\n%s", i, script)
		}
	}
}