// SPDX-License-Identifier: Apache-2.0
// Copyright 2026 alibaba/open-code-review Contributors

package main

import (
	"context"
	"encoding/json"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"

	"github.com/alibaba/open-code-review/internal/delegate"
)

func captureDelegateStdout(t *testing.T, fn func()) []byte {
	t.Helper()
	orig := os.Stdout
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatalf("create stdout pipe: %v", err)
	}
	os.Stdout = w
	defer func() { os.Stdout = orig }()

	// Drain while fn runs. Reading only after fn returns caps the capture at
	// whatever the pipe buffer holds: 64 KiB on Linux, far less on a Windows
	// anonymous pipe, and a payload past that blocks the writer forever.
	var out []byte
	var readErr error
	done := make(chan struct{})
	go func() {
		defer close(done)
		out, readErr = io.ReadAll(r)
	}()
	fn()
	if err := w.Close(); err != nil {
		t.Fatalf("close stdout writer: %v", err)
	}
	<-done
	if readErr != nil {
		t.Fatalf("read stdout: %v", readErr)
	}
	_ = r.Close()
	return out
}

// gitCommitFile writes a file and commits it, returning after the commit lands.
func gitCommitFile(t *testing.T, dir, name, content, msg string) {
	t.Helper()
	if err := os.WriteFile(filepath.Join(dir, name), []byte(content), 0o644); err != nil {
		t.Fatalf("write %s: %v", name, err)
	}
	for _, args := range [][]string{{"add", "."}, {"commit", "-m", msg}} {
		cmd := exec.Command("git", append([]string{"-C", dir}, args...)...)
		if out, err := cmd.CombinedOutput(); err != nil {
			t.Fatalf("git %v: %v: %s", args, err, out)
		}
	}
}

// silenceStdout redirects os.Stdout to /dev/null for the duration of fn so the
// delegate commands' Printf output does not clutter test logs.
func silenceStdout(t *testing.T, fn func()) {
	t.Helper()
	orig := os.Stdout
	devnull, err := os.OpenFile(os.DevNull, os.O_WRONLY, 0)
	if err != nil {
		t.Fatalf("open devnull: %v", err)
	}
	os.Stdout = devnull
	defer func() {
		os.Stdout = orig
		_ = devnull.Close()
	}()
	fn()
}

// freshOCRHome points the OCR home at a temp dir so a test can assert on what a
// command wrote there. It also neutralizes global git config: git resolves that
// via XDG_CONFIG_HOME as well, so overriding HOME alone would still pick up the
// developer's settings (e.g. commit.gpgsign, which fails without their keyring).
func freshOCRHome(t *testing.T) string {
	t.Helper()
	home := t.TempDir()
	t.Setenv("HOME", home)
	t.Setenv("GIT_CONFIG_GLOBAL", os.DevNull)
	t.Setenv("GIT_CONFIG_SYSTEM", os.DevNull)
	return home
}

// assertNoSessionStore fails if the session store was created under home.
// Preview neither runs nor finalizes a review, so it must not open persistence
// at all; session.New creates this directory before writing its JSONL file.
func assertNoSessionStore(t *testing.T, home string) {
	t.Helper()
	store := filepath.Join(home, ".opencodereview", "sessions")
	if _, err := os.Stat(store); !os.IsNotExist(err) {
		t.Errorf("preview created the session store at %s (stat err = %v)", store, err)
	}
}

func TestExecuteDelegatePreview_Workspace(t *testing.T) {
	dir := initTestGitRepo(t)
	// Uncommitted change so the workspace preview has at least one entry.
	if err := os.WriteFile(filepath.Join(dir, "app.go"), []byte("package app\n"), 0o644); err != nil {
		t.Fatalf("write app.go: %v", err)
	}
	silenceStdout(t, func() {
		if err := executeDelegatePreview(delegateOptions{repoDir: dir}); err != nil {
			t.Fatalf("executeDelegatePreview(workspace) error: %v", err)
		}
	})
}

func TestExecuteDelegatePreview_Range(t *testing.T) {
	dir := initTestGitRepo(t)
	gitCommitFile(t, dir, "b.go", "package b\n", "second commit")
	silenceStdout(t, func() {
		err := executeDelegatePreview(delegateOptions{repoDir: dir, from: "HEAD~1", to: "HEAD"})
		if err != nil {
			t.Fatalf("executeDelegatePreview(range) error: %v", err)
		}
	})
}

func TestExecuteDelegatePreview_Commit(t *testing.T) {
	dir := initTestGitRepo(t)
	gitCommitFile(t, dir, "c.go", "package c\n", "add c")
	silenceStdout(t, func() {
		// commit mode auto-fills background from the commit message.
		err := executeDelegatePreview(delegateOptions{repoDir: dir, commit: "HEAD"})
		if err != nil {
			t.Fatalf("executeDelegatePreview(commit) error: %v", err)
		}
	})
}

// TestExecuteDelegatePreviewCreatesNoSession covers the third preview entry
// point, which built its agent the same leaky way as review and scan.
func TestExecuteDelegatePreviewCreatesNoSession(t *testing.T) {
	home := freshOCRHome(t)

	dir := initTestGitRepo(t)
	gitCommitFile(t, dir, "d.go", "package d\n", "add d")
	silenceStdout(t, func() {
		if err := executeDelegatePreview(delegateOptions{repoDir: dir, commit: "HEAD"}); err != nil {
			t.Fatalf("executeDelegatePreview error: %v", err)
		}
	})

	assertNoSessionStore(t, home)
}

func TestExecuteDelegateRule(t *testing.T) {
	dir := initTestGitRepo(t)
	silenceStdout(t, func() {
		err := executeDelegateRule(delegateOptions{repoDir: dir}, []string{"README.md"})
		if err != nil {
			t.Fatalf("executeDelegateRule error: %v", err)
		}
	})
}

func TestExecuteDelegatePreviewJSON(t *testing.T) {
	dir := initTestGitRepo(t)
	if err := os.WriteFile(filepath.Join(dir, "app.go"), []byte("package app\n"), 0o644); err != nil {
		t.Fatalf("write app.go: %v", err)
	}
	out := captureDelegateStdout(t, func() {
		if err := executeDelegatePreview(delegateOptions{repoDir: dir, format: "json"}); err != nil {
			t.Fatalf("executeDelegatePreview(json) error: %v", err)
		}
	})
	var got delegatePreviewJSON
	if err := json.Unmarshal(out, &got); err != nil {
		t.Fatalf("decode preview JSON: %v\n%s", err, out)
	}
	if got.SchemaVersion != delegateSchemaVersion || got.Mode != "workspace" {
		t.Fatalf("unexpected envelope: %#v", got)
	}
	if len(got.ReviewableFiles) != 1 || got.ReviewableFiles[0].Path != "app.go" {
		t.Fatalf("reviewable_files = %#v", got.ReviewableFiles)
	}
	if got.ReviewableFiles == nil || got.ExcludedFiles == nil {
		t.Fatal("JSON arrays must not be null")
	}
}

func TestExecuteDelegateRuleJSON(t *testing.T) {
	dir := initTestGitRepo(t)
	out := captureDelegateStdout(t, func() {
		if err := executeDelegateRule(delegateOptions{repoDir: dir, format: "json"}, []string{"README.md"}); err != nil {
			t.Fatalf("executeDelegateRule(json) error: %v", err)
		}
	})
	var got delegateRulesJSON
	if err := json.Unmarshal(out, &got); err != nil {
		t.Fatalf("decode rules JSON: %v\n%s", err, out)
	}
	if got.SchemaVersion != delegateSchemaVersion || len(got.Groups) != 1 {
		t.Fatalf("unexpected rules envelope: %#v", got)
	}
	if len(got.Groups[0].Files) != 1 || got.Groups[0].Files[0] != "README.md" || got.Groups[0].Rule == "" {
		t.Fatalf("unexpected rule group: %#v", got.Groups[0])
	}
}

func TestRuleGroupsJSONEmptyFiles(t *testing.T) {
	groups := ruleGroupsJSON([]delegate.RuleGroup{{ID: 1}})
	if len(groups) != 1 {
		t.Fatalf("groups = %#v", groups)
	}
	if groups[0].Files == nil || len(groups[0].Files) != 0 {
		t.Fatalf("files must be an empty, non-nil slice: %#v", groups[0].Files)
	}
	payload, err := json.Marshal(groups[0])
	if err != nil {
		t.Fatalf("marshal rule group: %v", err)
	}
	if string(payload) == "" || !json.Valid(payload) {
		t.Fatalf("invalid JSON: %s", payload)
	}
	var decoded map[string]any
	if err := json.Unmarshal(payload, &decoded); err != nil {
		t.Fatalf("decode rule group: %v", err)
	}
	if files, ok := decoded["files"].([]any); !ok || len(files) != 0 {
		t.Fatalf("files JSON must be []: %s", payload)
	}
}

func TestLoadDelegateContext_BackgroundFile(t *testing.T) {
	dir := initTestGitRepo(t)
	bgPath := filepath.Join(dir, "bg.txt")
	if err := os.WriteFile(bgPath, []byte("extra background"), 0o644); err != nil {
		t.Fatalf("write bg: %v", err)
	}
	dc, err := loadDelegateContext(delegateOptions{repoDir: dir, backgroundFile: "bg.txt", background: "base"})
	if err != nil {
		t.Fatalf("loadDelegateContext error: %v", err)
	}
	if !strings.Contains(dc.opts.background, "extra background") {
		t.Errorf("expected file content to win, got %q", dc.opts.background)
	}
	if strings.Contains(dc.opts.background, "base") {
		t.Errorf("inline --background should be ignored when --background-file is set, got %q", dc.opts.background)
	}
}

func TestLoadDelegateContext_NotGitRepo(t *testing.T) {
	dir := t.TempDir()
	if _, err := loadDelegateContext(delegateOptions{repoDir: dir}); err == nil {
		t.Fatal("expected error for non-git dir")
	}
}

func TestDelegateContextMergeBase_Range(t *testing.T) {
	dir := initTestGitRepo(t)
	gitCommitFile(t, dir, "d.go", "package d\n", "add d")
	dc, err := loadDelegateContext(delegateOptions{repoDir: dir, from: "HEAD~1", to: "HEAD"})
	if err != nil {
		t.Fatalf("loadDelegateContext error: %v", err)
	}
	if got := dc.mergeBase(context.Background()); got == "" {
		t.Error("expected non-empty merge base for range mode")
	}
}