package main

import (
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

type syncFixture struct {
	root   string
	remote string
	work   string
	other  string
}

func makeSyncFixture(t *testing.T) syncFixture {
	t.Helper()
	root := t.TempDir()
	remote := filepath.Join(root, "remote.git")
	seed := filepath.Join(root, "seed")
	work := filepath.Join(root, "work")
	other := filepath.Join(root, "other")

	if err := os.MkdirAll(seed, 0o755); err != nil {
		t.Fatal(err)
	}
	git(t, root, "init", "--bare", "-q", "--initial-branch=main", remote)
	git(t, seed, "init", "-q", "--initial-branch=main")
	configureTestIdentity(t, seed)
	writeTestFile(t, filepath.Join(seed, "tracked.txt"), "initial\n")
	git(t, seed, "add", "tracked.txt")
	git(t, seed, "commit", "-qm", "initial")
	git(t, seed, "remote", "add", "origin", remote)
	git(t, seed, "push", "-qu", "origin", "main")

	git(t, root, "clone", "-q", remote, work)
	git(t, root, "clone", "-q", remote, other)
	configureTestIdentity(t, work)
	configureTestIdentity(t, other)

	git(t, work, "checkout", "-qb", "feature")
	writeTestFile(t, filepath.Join(work, "feature.txt"), "feature\n")
	git(t, work, "add", "feature.txt")
	git(t, work, "commit", "-qm", "feature")
	git(t, work, "push", "-qu", "origin", "feature")

	return syncFixture{root: root, remote: remote, work: work, other: other}
}

func configureTestIdentity(t *testing.T, path string) {
	t.Helper()
	git(t, path, "config", "user.name", "Test")
	git(t, path, "config", "user.email", "test@example.com")
}

func writeTestFile(t *testing.T, path, contents string) {
	t.Helper()
	if err := os.WriteFile(path, []byte(contents), 0o644); err != nil {
		t.Fatal(err)
	}
}

func advanceRemoteBranch(t *testing.T, fixture syncFixture, branch, filename string) {
	t.Helper()
	git(t, fixture.other, "fetch", "-q", "origin")
	git(t, fixture.other, "checkout", "-qB", branch, "origin/"+branch)
	writeTestFile(t, filepath.Join(fixture.other, filename), branch+" update\n")
	git(t, fixture.other, "add", filename)
	git(t, fixture.other, "commit", "-qm", "advance "+branch)
	git(t, fixture.other, "push", "-q", "origin", branch)
}

func gitText(t *testing.T, path string, args ...string) string {
	t.Helper()
	cmd := append([]string{"-C", path}, args...)
	output, err := exec.Command("git", cmd...).CombinedOutput()
	if err != nil {
		t.Fatalf("git %v: %v\n%s", args, err, output)
	}
	return strings.TrimSpace(string(output))
}

func TestDirtyFeatureBranchStillAllowsInactiveMainUpdate(t *testing.T) {
	fixture := makeSyncFixture(t)
	writeTestFile(t, filepath.Join(fixture.work, "local-notes.txt"), "unfinished work\n")
	advanceRemoteBranch(t, fixture, "main", "main-remote.txt")

	beforeFeature := gitText(t, fixture.work, "rev-parse", "feature")
	report, err := syncRepository(fixture.work, time.Minute, true, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}

	if got, want := gitText(t, fixture.work, "rev-parse", "main"), gitText(t, fixture.work, "rev-parse", "origin/main"); got != want {
		t.Fatalf("inactive main was not updated: got %s, want %s", got, want)
	}
	if got := gitText(t, fixture.work, "rev-parse", "feature"); got != beforeFeature {
		t.Fatalf("dirty checked-out feature branch moved: got %s, want %s", got, beforeFeature)
	}
	if got := gitText(t, fixture.work, "branch", "--show-current"); got != "feature" {
		t.Fatalf("checked-out branch = %q, want feature", got)
	}
	if _, err := os.Stat(filepath.Join(fixture.work, "local-notes.txt")); err != nil {
		t.Fatalf("dirty file was lost: %v", err)
	}
	assertBranchAction(t, report.Branches, "main", "updated")
}

func TestDirtyCheckedOutBranchIsProtectedWhenRemoteAdvances(t *testing.T) {
	fixture := makeSyncFixture(t)
	writeTestFile(t, filepath.Join(fixture.work, "feature.txt"), "unfinished feature edit\n")
	advanceRemoteBranch(t, fixture, "feature", "feature-remote.txt")
	before := gitText(t, fixture.work, "rev-parse", "feature")

	report, err := syncRepository(fixture.work, time.Minute, true, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}

	if got := gitText(t, fixture.work, "rev-parse", "feature"); got != before {
		t.Fatalf("dirty checked-out branch moved: got %s, want %s", got, before)
	}
	if upstream := gitText(t, fixture.work, "rev-parse", "origin/feature"); upstream == before {
		t.Fatal("fixture did not fetch the advanced remote feature branch")
	}
	contents, err := os.ReadFile(filepath.Join(fixture.work, "feature.txt"))
	if err != nil || string(contents) != "unfinished feature edit\n" {
		t.Fatalf("dirty edit changed: contents=%q err=%v", contents, err)
	}
	assertBranchAction(t, report.Branches, "feature", "protected")
}

func TestCleanCheckedOutBranchFastForwards(t *testing.T) {
	fixture := makeSyncFixture(t)
	advanceRemoteBranch(t, fixture, "feature", "feature-remote.txt")

	report, err := syncRepository(fixture.work, time.Minute, false, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}
	if got, want := gitText(t, fixture.work, "rev-parse", "feature"), gitText(t, fixture.work, "rev-parse", "origin/feature"); got != want {
		t.Fatalf("checked-out feature was not fast-forwarded: got %s, want %s", got, want)
	}
	if _, err := os.Stat(filepath.Join(fixture.work, "feature-remote.txt")); err != nil {
		t.Fatalf("fast-forwarded file is missing from worktree: %v", err)
	}
	assertBranchAction(t, report.Branches, "feature", "updated")
}

func TestDivergentBranchIsWarnedAndLeftUnchanged(t *testing.T) {
	fixture := makeSyncFixture(t)
	writeTestFile(t, filepath.Join(fixture.work, "local-only.txt"), "local commit\n")
	git(t, fixture.work, "add", "local-only.txt")
	git(t, fixture.work, "commit", "-qm", "local feature work")
	localOID := gitText(t, fixture.work, "rev-parse", "feature")
	advanceRemoteBranch(t, fixture, "feature", "remote-only.txt")

	report, err := syncRepository(fixture.work, time.Minute, false, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}
	if got := gitText(t, fixture.work, "rev-parse", "feature"); got != localOID {
		t.Fatalf("divergent feature branch moved: got %s, want %s", got, localOID)
	}
	assertBranchAction(t, report.Branches, "feature", "warning")
}

func TestMergedInactiveBranchWithDeletedUpstreamIsDeleted(t *testing.T) {
	fixture := makeSyncFixture(t)
	git(t, fixture.work, "branch", "old", "main")
	git(t, fixture.work, "push", "-qu", "origin", "old")
	git(t, fixture.work, "push", "-q", "origin", "--delete", "old")

	report, err := syncRepository(fixture.work, time.Minute, false, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}
	if err := exec.Command("git", "-C", fixture.work, "show-ref", "--verify", "--quiet", "refs/heads/old").Run(); err == nil {
		t.Fatal("merged branch with deleted configured upstream still exists")
	}
	assertBranchAction(t, report.Branches, "old", "deleted")
}

func TestBranchCheckedOutInAnotherWorktreeIsProtected(t *testing.T) {
	fixture := makeSyncFixture(t)
	mainWorktree := filepath.Join(fixture.root, "main-worktree")
	git(t, fixture.work, "worktree", "add", "-q", mainWorktree, "main")
	before := gitText(t, fixture.work, "rev-parse", "main")
	advanceRemoteBranch(t, fixture, "main", "main-remote.txt")

	report, err := syncRepository(fixture.work, time.Minute, false, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}
	if got := gitText(t, fixture.work, "rev-parse", "main"); got != before {
		t.Fatalf("branch checked out in another worktree moved: got %s, want %s", got, before)
	}
	assertBranchAction(t, report.Branches, "main", "protected")
}

func assertBranchAction(t *testing.T, results []branchSyncResult, branch, action string) {
	t.Helper()
	for _, result := range results {
		if result.Branch == branch && result.Action == action {
			return
		}
	}
	t.Fatalf("missing %s action for branch %s in %+v", action, branch, results)
}

// A local branch with neither a configured upstream nor a same-named branch on
// the remote cannot be fast-forwarded. It used to be dropped from the report
// entirely, so the run claimed "Already up to date" while doing nothing at all.
func TestLocalBranchWithoutUpstreamIsReportedNotSilentlyDropped(t *testing.T) {
	fixture := makeSyncFixture(t)
	git(t, fixture.work, "branch", "stray", "main")
	strayBefore := gitText(t, fixture.work, "rev-parse", "stray")
	advanceRemoteBranch(t, fixture, "main", "main-remote.txt")

	report, err := syncRepository(fixture.work, time.Minute, false, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}
	assertBranchAction(t, report.Branches, "stray", "untracked")
	if report.Message == "Already up to date." {
		t.Fatalf("report claimed to be up to date while a branch was left alone: %q", report.Message)
	}
	// The untracked branch must genuinely be left untouched, even though a
	// sibling branch in the same run did move.
	if got := gitText(t, fixture.work, "rev-parse", "stray"); got != strayBefore {
		t.Fatalf("stray moved: got %s, want %s", got, strayBefore)
	}
	// A branch it *can* fix is still fixed in the same run.
	if got, want := gitText(t, fixture.work, "rev-parse", "main"), gitText(t, fixture.work, "rev-parse", "origin/main"); got != want {
		t.Fatalf("inactive main was not updated: got %s, want %s", got, want)
	}
}

func TestRemoteBranchWithoutLocalCounterpartIsCreated(t *testing.T) {
	fixture := makeSyncFixture(t)
	git(t, fixture.work, "push", "-qu", "origin", "main:refs/heads/brand-new")

	report, err := syncRepositoryWith(fixture.work, time.Minute, false, nil, syncOptions{CreateMissing: true})
	if err != nil {
		t.Fatalf("syncRepositoryWith(): %v\n%s", err, report.Message)
	}
	assertBranchAction(t, report.Branches, "brand-new", "created")
	if got, want := gitText(t, fixture.work, "rev-parse", "brand-new"), gitText(t, fixture.work, "rev-parse", "origin/main"); got != want {
		t.Fatalf("created branch is at the wrong commit: got %s, want %s", got, want)
	}
	if upstream := gitText(t, fixture.work, "rev-parse", "--abbrev-ref", "brand-new@{upstream}"); upstream != "origin/brand-new" {
		t.Fatalf("created branch upstream = %q, want origin/brand-new", upstream)
	}
	// Creating a branch must never move the branch that is checked out.
	if got := gitText(t, fixture.work, "branch", "--show-current"); got != "feature" {
		t.Fatalf("checked-out branch = %q, want feature", got)
	}
}

// Like hub, stack-sync does not create remote-only branches unless asked.
func TestRemoteBranchIsNotCreatedByDefault(t *testing.T) {
	fixture := makeSyncFixture(t)
	git(t, fixture.work, "push", "-qu", "origin", "main:refs/heads/brand-new")

	if _, err := syncRepositoryWith(fixture.work, time.Minute, false, nil, syncOptions{CreateMissing: false}); err != nil {
		t.Fatalf("syncRepositoryWith(): %v", err)
	}
	if err := exec.Command("git", "-C", fixture.work, "show-ref", "--verify", "--quiet", "refs/heads/brand-new").Run(); err == nil {
		t.Fatal("brand-new was created even though CreateMissing is false")
	}

	// The zero value of syncOptions must also mean "do not create".
	if _, err := syncRepository(fixture.work, time.Minute, false, nil); err != nil {
		t.Fatalf("syncRepository(): %v", err)
	}
	if err := exec.Command("git", "-C", fixture.work, "show-ref", "--verify", "--quiet", "refs/heads/brand-new").Run(); err == nil {
		t.Fatal("brand-new was created by the default syncRepository()")
	}
}

// The flag is opt-in. Guard against the default silently flipping back on, which
// previously happened because the value was resolved before flags were parsed.
func TestCreateMissingFlagIsOptIn(t *testing.T) {
	opts, err := parseFlags("sync", nil, io.Discard)
	if err != nil {
		t.Fatalf("parseFlags(): %v", err)
	}
	if opts.createMissing {
		t.Fatal("--create-missing must default to false")
	}
	opts, err = parseFlags("sync", []string{"--create-missing"}, io.Discard)
	if err != nil {
		t.Fatalf("parseFlags(): %v", err)
	}
	if !opts.createMissing {
		t.Fatal("--create-missing did not enable branch creation")
	}
}

// git shortens refs/remotes/origin/HEAD to the shortest unambiguous form, which
// is plain "origin". Treating that as a branch name produced a bogus
// "create branch origin" failure.
func TestRemoteHeadSymrefIsNotListedAsABranch(t *testing.T) {
	fixture := makeSyncFixture(t)
	git(t, fixture.work, "fetch", "-q", "origin")

	branches, err := remoteTrackingBranches(t.Context(), fixture.work, "origin")
	if err != nil {
		t.Fatalf("remoteTrackingBranches(): %v", err)
	}
	var names []string
	for _, branch := range branches {
		names = append(names, branch.name)
		if branch.name == "origin" || branch.name == "HEAD" {
			t.Fatalf("remote HEAD symref leaked into the branch list as %q: %v", branch.name, names)
		}
	}
	if len(names) == 0 {
		t.Fatal("expected the remote's real branches to be listed")
	}
}

// refs/remotes/<remote>/HEAD is a local convenience symref and is missing from
// plenty of real clones. Without resolving the default branch another way, merged
// branches with a deleted upstream were kept with a vague warning.
func TestRemoteDefaultBranchFallsBackToAskingTheRemote(t *testing.T) {
	fixture := makeSyncFixture(t)
	git(t, fixture.work, "remote", "set-head", "origin", "-d")
	if err := exec.Command("git", "-C", fixture.work, "symbolic-ref", "--quiet", "--verify", "refs/remotes/origin/HEAD").Run(); err == nil {
		t.Skip("git kept the remote HEAD symref; fallback not exercised")
	}

	ref, branch, err := remoteDefaultBranch(t.Context(), fixture.work, "origin")
	if err != nil {
		t.Fatalf("remoteDefaultBranch(): %v", err)
	}
	if branch != "main" {
		t.Fatalf("default branch = %q, want main", branch)
	}
	if ref == "" {
		t.Fatal("remoteDefaultBranch() returned no ref")
	}
}

func TestMergedBranchIsDeletedWhenRemoteHeadSymrefIsMissing(t *testing.T) {
	fixture := makeSyncFixture(t)
	git(t, fixture.work, "branch", "old", "main")
	git(t, fixture.work, "push", "-qu", "origin", "old")
	git(t, fixture.work, "push", "-q", "origin", "--delete", "old")
	git(t, fixture.work, "remote", "set-head", "origin", "-d")

	report, err := syncRepository(fixture.work, time.Minute, false, nil)
	if err != nil {
		t.Fatalf("syncRepository(): %v\n%s", err, report.Message)
	}
	if err := exec.Command("git", "-C", fixture.work, "show-ref", "--verify", "--quiet", "refs/heads/old").Run(); err == nil {
		t.Fatalf("merged branch was kept without origin/HEAD: %s", report.Message)
	}
	assertBranchAction(t, report.Branches, "old", "deleted")
}