package overlay

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

	"sub2api-cn-relay-manager/internal/pack"
)

func TestApplyCopiesSourceAndAppliesPatch(t *testing.T) {
	sourceDir := t.TempDir()
	if err := os.MkdirAll(filepath.Join(sourceDir, "backend"), 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(sourceDir, "backend", "hello.txt"), []byte("hello\n"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}

	packDir := t.TempDir()
	patchBody := strings.Join([]string{
		"diff --git a/backend/hello.txt b/backend/hello.txt",
		"--- a/backend/hello.txt",
		"+++ b/backend/hello.txt",
		"@@ -1 +1 @@",
		"-hello",
		"+patched",
		"",
	}, "\n")
	patchPath := filepath.Join(packDir, "overlays", "sample.patch")
	if err := os.MkdirAll(filepath.Dir(patchPath), 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	if err := os.WriteFile(patchPath, []byte(patchBody), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}

	result, err := Apply(context.Background(), ApplyRequest{
		PackDir:   packDir,
		SourceDir: sourceDir,
		Overlays: []pack.HostOverlay{{
			OverlayID: "sample",
			PatchPath: "overlays/sample.patch",
		}},
	})
	if err != nil {
		t.Fatalf("Apply() error = %v", err)
	}
	body, err := os.ReadFile(filepath.Join(result.OutputDir, "backend", "hello.txt"))
	if err != nil {
		t.Fatalf("ReadFile() error = %v", err)
	}
	if string(body) != "patched\n" {
		t.Fatalf("patched file = %q, want %q", string(body), "patched\n")
	}
	if _, err := os.Stat(result.MetadataFilePath); err != nil {
		t.Fatalf("Stat(metadata) error = %v", err)
	}
}

func TestApplySupportsRelativePackDir(t *testing.T) {
	workspaceDir := t.TempDir()
	originalWD, err := os.Getwd()
	if err != nil {
		t.Fatalf("Getwd() error = %v", err)
	}
	if err := os.Chdir(workspaceDir); err != nil {
		t.Fatalf("Chdir() error = %v", err)
	}
	t.Cleanup(func() {
		_ = os.Chdir(originalWD)
	})

	sourceDir := filepath.Join(workspaceDir, "source")
	if err := os.MkdirAll(filepath.Join(sourceDir, "backend"), 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(sourceDir, "backend", "hello.txt"), []byte("hello\n"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}

	packDir := filepath.Join(workspaceDir, "pack")
	patchPath := filepath.Join(packDir, "overlays", "sample.patch")
	if err := os.MkdirAll(filepath.Dir(patchPath), 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	patchBody := strings.Join([]string{
		"diff --git a/backend/hello.txt b/backend/hello.txt",
		"--- a/backend/hello.txt",
		"+++ b/backend/hello.txt",
		"@@ -1 +1 @@",
		"-hello",
		"+patched",
		"",
	}, "\n")
	if err := os.WriteFile(patchPath, []byte(patchBody), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}

	result, err := Apply(context.Background(), ApplyRequest{
		PackDir:   "pack",
		SourceDir: sourceDir,
		Overlays: []pack.HostOverlay{{
			OverlayID: "sample",
			PatchPath: "overlays/sample.patch",
		}},
	})
	if err != nil {
		t.Fatalf("Apply() with relative pack dir error = %v", err)
	}
	body, err := os.ReadFile(filepath.Join(result.OutputDir, "backend", "hello.txt"))
	if err != nil {
		t.Fatalf("ReadFile() error = %v", err)
	}
	if string(body) != "patched\n" {
		t.Fatalf("patched file = %q, want %q", string(body), "patched\n")
	}
}

func TestFilterOverlaysRejectsMissingOverlayID(t *testing.T) {
	_, err := FilterOverlays([]pack.HostOverlay{{OverlayID: "sample"}}, "missing")
	if err == nil || !strings.Contains(err.Error(), `overlay "missing" did not match`) {
		t.Fatalf("FilterOverlays() error = %v, want missing overlay detail", err)
	}
}

func TestApplyRejectsNestedOutputDir(t *testing.T) {
	sourceDir := t.TempDir()
	if err := os.MkdirAll(filepath.Join(sourceDir, "backend"), 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}

	_, err := Apply(context.Background(), ApplyRequest{
		PackDir:   t.TempDir(),
		SourceDir: sourceDir,
		OutputDir: filepath.Join(sourceDir, "nested-output"),
		Overlays:  []pack.HostOverlay{{OverlayID: "sample", PatchPath: "overlays/sample.patch"}},
	})
	if err == nil || !strings.Contains(err.Error(), "must not be nested inside source dir") {
		t.Fatalf("Apply() error = %v, want nested output rejection", err)
	}
}

func TestApplyPatchFileRejectsMissingPatch(t *testing.T) {
	err := applyPatchFile(context.Background(), t.TempDir(), filepath.Join(t.TempDir(), "missing.patch"))
	if err == nil || !strings.Contains(err.Error(), "stat patch file") {
		t.Fatalf("applyPatchFile() error = %v, want missing patch stat error", err)
	}
}

func TestApplyPatchFileRejectsInvalidPatch(t *testing.T) {
	outputDir := t.TempDir()
	patchPath := filepath.Join(t.TempDir(), "invalid.patch")
	if err := os.WriteFile(patchPath, []byte("not a patch\n"), 0o644); err != nil {
		t.Fatalf("WriteFile() error = %v", err)
	}

	err := applyPatchFile(context.Background(), outputDir, patchPath)
	if err == nil {
		t.Fatal("applyPatchFile() error = nil, want invalid patch failure")
	}
}

func TestWriteMetadataIncludesSourceDirAndOverlays(t *testing.T) {
	metadataPath := filepath.Join(t.TempDir(), metadataFileName)
	overlays := []pack.HostOverlay{{OverlayID: "sample", PatchPath: "overlays/sample.patch"}}
	if err := writeMetadata(metadataPath, "/tmp/source", overlays); err != nil {
		t.Fatalf("writeMetadata() error = %v", err)
	}

	body, err := os.ReadFile(metadataPath)
	if err != nil {
		t.Fatalf("ReadFile() error = %v", err)
	}
	var decoded map[string]any
	if err := json.Unmarshal(body, &decoded); err != nil {
		t.Fatalf("json.Unmarshal() error = %v", err)
	}
	if got, _ := decoded["source_dir"].(string); got != "/tmp/source" {
		t.Fatalf("source_dir = %q, want %q", got, "/tmp/source")
	}
	applied, ok := decoded["applied_overlays"].([]any)
	if !ok || len(applied) != 1 {
		t.Fatalf("applied_overlays = %#v, want one overlay", decoded["applied_overlays"])
	}
}

func TestCopyTreeSkipsGitAndPreservesSymlink(t *testing.T) {
	sourceDir := t.TempDir()
	outputDir := filepath.Join(t.TempDir(), "output")
	if err := os.MkdirAll(filepath.Join(sourceDir, ".git", "objects"), 0o755); err != nil {
		t.Fatalf("MkdirAll(.git) error = %v", err)
	}
	if err := os.MkdirAll(filepath.Join(sourceDir, "backend"), 0o755); err != nil {
		t.Fatalf("MkdirAll(backend) error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(sourceDir, ".git", "config"), []byte("ignored"), 0o644); err != nil {
		t.Fatalf("WriteFile(.git/config) error = %v", err)
	}
	if err := os.WriteFile(filepath.Join(sourceDir, "backend", "hello.txt"), []byte("hello\n"), 0o644); err != nil {
		t.Fatalf("WriteFile(hello.txt) error = %v", err)
	}
	if err := os.Symlink(filepath.Join("backend", "hello.txt"), filepath.Join(sourceDir, "hello-link")); err != nil {
		t.Fatalf("Symlink() error = %v", err)
	}

	if err := copyTree(sourceDir, outputDir); err != nil {
		t.Fatalf("copyTree() error = %v", err)
	}
	if _, err := os.Stat(filepath.Join(outputDir, ".git", "config")); !os.IsNotExist(err) {
		t.Fatalf("output .git/config error = %v, want not exist", err)
	}
	target, err := os.Readlink(filepath.Join(outputDir, "hello-link"))
	if err != nil {
		t.Fatalf("Readlink() error = %v", err)
	}
	if target != filepath.Join("backend", "hello.txt") {
		t.Fatalf("symlink target = %q, want backend/hello.txt", target)
	}
}

func TestApplyRejectsExistingOutputDir(t *testing.T) {
	sourceDir := t.TempDir()
	if err := os.MkdirAll(filepath.Join(sourceDir, "backend"), 0o755); err != nil {
		t.Fatalf("MkdirAll() error = %v", err)
	}
	outputDir := filepath.Join(t.TempDir(), "existing-output")
	if err := os.MkdirAll(outputDir, 0o755); err != nil {
		t.Fatalf("MkdirAll(outputDir) error = %v", err)
	}

	_, err := Apply(context.Background(), ApplyRequest{
		PackDir:   t.TempDir(),
		SourceDir: sourceDir,
		OutputDir: outputDir,
		Overlays:  []pack.HostOverlay{{OverlayID: "sample", PatchPath: "overlays/sample.patch"}},
	})
	if err == nil || !strings.Contains(err.Error(), "already exists") {
		t.Fatalf("Apply() error = %v, want existing output rejection", err)
	}
}

func TestCopyFileRejectsMissingSource(t *testing.T) {
	err := copyFile(filepath.Join(t.TempDir(), "missing.txt"), filepath.Join(t.TempDir(), "target.txt"), 0o644)
	if err == nil {
		t.Fatal("copyFile() error = nil, want missing source failure")
	}
}