package releasekit_test

import (
	"bytes"
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"hash"
	"io"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"testing"

	releasekit "gitea.maximumdirect.net/eric/ReleaseKit"
	"gitea.maximumdirect.net/eric/ReleaseKit/internal/gitea"
)

const performanceDeliveryArtifactSize = 16 << 20

type deliveryBenchmarkAsset struct {
	name   string
	data   []byte
	digest string
}

type deliveryBenchmarkServer struct {
	mu       sync.Mutex
	baseURL  string
	commit   string
	assets   []deliveryBenchmarkAsset
	page     bool
	attached map[string]deliveryBenchmarkIdentity
}

type deliveryBenchmarkIdentity struct {
	digest string
	size   int64
}

func BenchmarkPerformanceFacadeDeliver(b *testing.B) {
	repository, build, expected := newDeliveryBenchmarkFixture(b)
	state := &deliveryBenchmarkServer{commit: gitText(b, repository, "rev-parse", "HEAD"), assets: expected}
	server := httptest.NewServer(http.HandlerFunc(state.serveHTTP))
	state.baseURL = server.URL
	b.Cleanup(server.Close)
	request := releasekit.DeliveryRequest{
		RepositoryDir: repository,
		Product:       "Sample App",
		Version:       "v1.2.3",
		Destination:   facadeDeliveryDestination(server.URL),
		Prebuilt:      &build,
	}
	totalBytes := int64(2 * performanceDeliveryArtifactSize)

	b.Run("FreshUploads", func(b *testing.B) {
		b.ReportAllocs()
		b.SetBytes(totalBytes)
		b.ReportMetric(float64(totalBytes), "artifact-bytes/op")
		b.ReportMetric(2, "binary-files/op")
		for i := 0; i < b.N; i++ {
			b.StopTimer()
			state.reset(false)
			b.StartTimer()
			result, err := releasekit.Deliver(context.Background(), request)
			b.StopTimer()
			if err != nil {
				b.Fatalf("Deliver() error = %v", err)
			}
			if len(result.Uploaded) != 3 {
				b.Fatalf("uploaded %d assets, want two binaries and a manifest", len(result.Uploaded))
			}
			state.verifyUploads(b)
			b.StartTimer()
		}
	})

	b.Run("MatchingRetry", func(b *testing.B) {
		b.StopTimer()
		state.reset(true)
		b.ReportAllocs()
		b.SetBytes(totalBytes)
		b.ReportMetric(float64(totalBytes), "artifact-bytes/op")
		b.ReportMetric(2, "binary-files/op")
		b.ResetTimer()
		b.StartTimer()
		for i := 0; i < b.N; i++ {
			result, err := releasekit.Deliver(context.Background(), request)
			if err != nil {
				b.Fatalf("Deliver() error = %v", err)
			}
			if len(result.Uploaded) != 0 || len(result.Matching) != 3 {
				b.Fatalf("matching retry uploaded %d and matched %d assets; want 0 and 3", len(result.Uploaded), len(result.Matching))
			}
		}
	})
}

func newDeliveryBenchmarkFixture(b testing.TB) (string, releasekit.BuildResult, []deliveryBenchmarkAsset) {
	b.Helper()
	repository := filepath.Join(b.TempDir(), "repository")
	if err := os.MkdirAll(repository, 0o755); err != nil {
		b.Fatal(err)
	}
	gitRun(b, repository, "init", "-b", "main")
	gitRun(b, repository, "config", "user.name", "ReleaseKit Benchmark")
	gitRun(b, repository, "config", "user.email", "benchmark@example.invalid")
	writeFile(b, repository, "go.mod", "module example.com/deliveryfixture\n\ngo 1.26.0\n")
	writeFile(b, repository, "docs/releases/v1.2.3.md", "# Sample App v1.2.3\n\nDelivery fixture.\n")
	gitRun(b, repository, "add", ".")
	gitRun(b, repository, "commit", "-m", "prepare delivery benchmark")
	gitRun(b, repository, "tag", "v1.2.3")

	data := make([]byte, performanceDeliveryArtifactSize)
	for i := range data {
		data[i] = byte((i*17 + i/127 + 29) % 251)
	}
	digest := sha256.Sum256(data)
	digestText := hex.EncodeToString(digest[:])
	outputDir := filepath.Join(b.TempDir(), "artifacts")
	if err := os.MkdirAll(outputDir, 0o700); err != nil {
		b.Fatal(err)
	}
	targets := []releasekit.Target{{OS: "linux", Arch: "amd64"}, {OS: "windows", Arch: "amd64"}}
	build := releasekit.BuildResult{
		RepositoryDir: repository, CandidateCommit: gitText(b, repository, "rev-parse", "HEAD"),
		ModuleDir: repository, ModulePath: "example.com/deliveryfixture", Tag: "v1.2.3",
		SourceVerified: true, Version: "v1.2.3", MainPackage: "./cmd/app",
		BinaryName: "releasekit", Targets: targets, OutputDir: outputDir,
	}
	assets := make([]deliveryBenchmarkAsset, 0, len(targets)+1)
	for _, target := range targets {
		filename := fmt.Sprintf("releasekit-v1.2.3-%s-%s", target.OS, target.Arch)
		if target.OS == "windows" {
			filename += ".exe"
		}
		path := filepath.Join(outputDir, filename)
		if err := os.WriteFile(path, data, 0o600); err != nil {
			b.Fatal(err)
		}
		build.Artifacts = append(build.Artifacts, releasekit.BuildArtifact{Path: path, Filename: filename, Target: target, SHA256: digestText})
		assets = append(assets, deliveryBenchmarkAsset{name: filename, data: data, digest: digestText})
	}
	manifest := performanceDeliveryManifest(build.Artifacts)
	manifestHash := sha256.Sum256(manifest)
	assets = append(assets, deliveryBenchmarkAsset{name: gitea.ManifestFilename, data: manifest, digest: hex.EncodeToString(manifestHash[:])})
	return repository, build, assets
}

func performanceDeliveryManifest(artifacts []releasekit.BuildArtifact) []byte {
	ordered := append([]releasekit.BuildArtifact(nil), artifacts...)
	sort.Slice(ordered, func(i, j int) bool { return ordered[i].Filename < ordered[j].Filename })
	var manifest strings.Builder
	for _, artifact := range ordered {
		fmt.Fprintf(&manifest, "%s  %s\n", artifact.SHA256, artifact.Filename)
	}
	return []byte(manifest.String())
}

func (state *deliveryBenchmarkServer) reset(populated bool) {
	state.mu.Lock()
	defer state.mu.Unlock()
	state.page = populated
	state.attached = make(map[string]deliveryBenchmarkIdentity)
	if populated {
		for _, asset := range state.assets {
			state.attached[asset.name] = deliveryBenchmarkIdentity{digest: asset.digest, size: int64(len(asset.data))}
		}
	}
}

func (state *deliveryBenchmarkServer) verifyUploads(b testing.TB) {
	b.Helper()
	state.mu.Lock()
	defer state.mu.Unlock()
	if !state.page || len(state.attached) != len(state.assets) {
		b.Fatalf("fresh upload left release page %t and %d attached assets, want page and %d assets", state.page, len(state.attached), len(state.assets))
	}
	for _, asset := range state.assets {
		identity, ok := state.attached[asset.name]
		if !ok || identity.digest != asset.digest || identity.size != int64(len(asset.data)) {
			b.Fatalf("uploaded %q identity = %#v, present %t; want digest %s and size %d", asset.name, identity, ok, asset.digest, len(asset.data))
		}
	}
}

func (state *deliveryBenchmarkServer) serveHTTP(w http.ResponseWriter, r *http.Request) {
	switch r.URL.Path {
	case "/api/v1/repos/owner/example/tags/v1.2.3":
		_, _ = fmt.Fprintf(w, `{"name":"v1.2.3","commit":{"sha":%q}}`, state.commit)
	case "/api/v1/repos/owner/example/releases/tags/v1.2.3":
		state.mu.Lock()
		page := state.page
		state.mu.Unlock()
		if !page {
			http.NotFound(w, r)
			return
		}
		state.writeRelease(w)
	case "/api/v1/repos/owner/example/releases":
		state.mu.Lock()
		state.page = true
		state.mu.Unlock()
		state.writeRelease(w)
	case "/api/v1/repos/owner/example/releases/10/assets":
		if r.Method == http.MethodGet {
			state.writeAssetList(w)
			return
		}
		state.receiveUpload(w, r)
	default:
		if strings.HasPrefix(r.URL.Path, "/files/") {
			state.serveFile(w, r)
			return
		}
		http.NotFound(w, r)
	}
}

func (state *deliveryBenchmarkServer) writeRelease(w http.ResponseWriter) {
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(map[string]any{
		"id": 10, "html_url": state.baseURL + "/releases/10", "tag_name": "v1.2.3",
		"target_commitish": state.commit, "name": "Fixture v1.2.3",
		"body": "# Sample App v1.2.3\n\nDelivery fixture.\n", "draft": false, "prerelease": false,
	})
}

func (state *deliveryBenchmarkServer) writeAssetList(w http.ResponseWriter) {
	state.mu.Lock()
	assets := make([]map[string]any, 0, len(state.attached))
	for name, identity := range state.attached {
		assets = append(assets, map[string]any{
			"id": len(assets) + 1, "name": name, "size": identity.size,
			"browser_download_url": state.baseURL + "/files/" + name,
		})
	}
	state.mu.Unlock()
	_ = json.NewEncoder(w).Encode(assets)
}

func (state *deliveryBenchmarkServer) receiveUpload(w http.ResponseWriter, r *http.Request) {
	name := r.URL.Query().Get("name")
	reader, err := r.MultipartReader()
	if err != nil {
		http.Error(w, "invalid multipart request", http.StatusBadRequest)
		return
	}
	var digest hash.Hash = sha256.New()
	var size int64
	for {
		part, err := reader.NextPart()
		if err == io.EOF {
			break
		}
		if err != nil {
			http.Error(w, "invalid multipart body", http.StatusBadRequest)
			return
		}
		if part.FormName() == "attachment" {
			size, err = io.Copy(digest, part)
			if err != nil {
				_ = part.Close()
				http.Error(w, "cannot read attachment", http.StatusBadRequest)
				return
			}
		}
		_ = part.Close()
	}
	identity := deliveryBenchmarkIdentity{digest: hex.EncodeToString(digest.Sum(nil)), size: size}
	var expected *deliveryBenchmarkAsset
	for i := range state.assets {
		if state.assets[i].name == name {
			expected = &state.assets[i]
			break
		}
	}
	if expected == nil || identity.digest != expected.digest || identity.size != int64(len(expected.data)) {
		http.Error(w, "attachment digest or size mismatch", http.StatusBadRequest)
		return
	}
	state.mu.Lock()
	state.attached[name] = identity
	assetID := len(state.attached)
	state.mu.Unlock()
	w.WriteHeader(http.StatusCreated)
	_ = json.NewEncoder(w).Encode(map[string]any{"id": assetID, "name": name, "size": size})
}

func (state *deliveryBenchmarkServer) serveFile(w http.ResponseWriter, r *http.Request) {
	name := strings.TrimPrefix(r.URL.Path, "/files/")
	for _, asset := range state.assets {
		if asset.name == name {
			w.Header().Set("Content-Length", fmt.Sprint(len(asset.data)))
			_, _ = io.Copy(w, bytes.NewReader(asset.data))
			return
		}
	}
	http.NotFound(w, r)
}