package depot

import (
	"context"
	"crypto/sha256"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"testing"
	"time"
)

func shaOf(s string) string {
	return fmt.Sprintf("%x", sha256.Sum256([]byte(s)))
}

type recordedReq struct {
	Method  string
	Path    string
	Range   string
	Headers http.Header
}

// fakeBunny is a minimal recording fake for Bunny storage/CDN endpoints.
type fakeBunny struct {
	mu        sync.Mutex
	requests  []recordedReq
	headCount int
	blobs     map[string][]byte
	statusFor map[string]int // sha -> status code override for probe/get
}

func newFakeBunny() *fakeBunny {
	return &fakeBunny{blobs: map[string][]byte{}, statusFor: map[string]int{}}
}

func (f *fakeBunny) handler() http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		f.mu.Lock()
		f.requests = append(f.requests, recordedReq{
			Method:  r.Method,
			Path:    r.URL.Path,
			Range:   r.Header.Get("Range"),
			Headers: r.Header.Clone(),
		})
		if r.Method == http.MethodHead {
			f.headCount++
			f.mu.Unlock()
			w.WriteHeader(500)
			return
		}
		f.mu.Unlock()

		sha := strings.TrimPrefix(r.URL.Path, "/")
		// last path element is the sha
		parts := strings.Split(sha, "/")
		sha = parts[len(parts)-1]

		if r.Method == http.MethodPut {
			buf, _ := io.ReadAll(r.Body)
			f.mu.Lock()
			f.blobs[sha] = buf
			f.mu.Unlock()
			w.WriteHeader(201)
			return
		}

		// GET (range probe / actual get)
		f.mu.Lock()
		status, hasStatus := f.statusFor[sha]
		data, ok := f.blobs[sha]
		f.mu.Unlock()

		if hasStatus {
			w.WriteHeader(status)
			return
		}
		if !ok {
			w.WriteHeader(404)
			return
		}
		w.WriteHeader(206)
		_, _ = w.Write(data)
	}
}

func (f *fakeBunny) requestsSnapshot() []recordedReq {
	f.mu.Lock()
	defer f.mu.Unlock()
	out := make([]recordedReq, len(f.requests))
	copy(out, f.requests)
	return out
}

func testCfg(storageHost, readKey, writeKey string) Config {
	return Config{
		CDNBase:        "http://127.0.0.1:1", // unreachable by default; overridden per test
		StorageHost:    storageHost,
		StorageZone:    "sow-assets-depot",
		ReadKey:        readKey,
		WriteKey:       writeKey,
		ProbeJobs:      4,
		Jobs:           4,
		ConnectTimeout: 2 * time.Second,
		ProbeMaxTime:   2 * time.Second,
		ConfirmRetries: 3,
		ConfirmMax:     200,
	}
}

// hostPort returns a StorageHost value for tests: a full "http://host:port"
// base URL, which storageURL() passes through unchanged (bypassing the
// production https:// default so httptest.NewServer works without TLS).
func hostPort(srv *httptest.Server) string {
	return srv.URL
}

func TestProbeUsesRangeGetNotHead(t *testing.T) {
	sha := shaOf("present-blob")
	f := newFakeBunny()
	f.blobs[sha] = []byte("hello")
	srv := httptest.NewServer(f.handler())
	defer srv.Close()

	cfg := testCfg(hostPort(srv), "readkey", "writekey")
	b, err := NewBackend("bunny", "", cfg)
	if err != nil {
		t.Fatalf("NewBackend: %v", err)
	}

	state, transient, err := b.Probe(context.Background(), sha)
	if err != nil {
		t.Fatalf("Probe: %v", err)
	}
	if state != Present || transient {
		t.Fatalf("expected Present/non-transient, got %v/%v", state, transient)
	}

	reqs := f.requestsSnapshot()
	if len(reqs) != 1 {
		t.Fatalf("expected exactly 1 request, got %d", len(reqs))
	}
	if reqs[0].Method != "GET" {
		t.Fatalf("expected GET, got %s", reqs[0].Method)
	}
	if reqs[0].Range != "bytes=0-0" {
		t.Fatalf("expected Range bytes=0-0, got %q", reqs[0].Range)
	}
	if f.headCount != 0 {
		t.Fatalf("expected zero HEAD requests, got %d", f.headCount)
	}
}

func TestProbeStates(t *testing.T) {
	cases := []struct {
		status        int
		wantState     ProbeState
		wantTransient bool
	}{
		{200, Present, false},
		{206, Present, false},
		{404, Absent, false},
		{428, Unconfirmed, true},
		{503, Unconfirmed, true},
	}

	for _, c := range cases {
		t.Run(fmt.Sprintf("status_%d", c.status), func(t *testing.T) {
			sha := shaOf(fmt.Sprintf("blob-%d", c.status))
			f := newFakeBunny()
			f.statusFor[sha] = c.status
			srv := httptest.NewServer(f.handler())
			defer srv.Close()

			cfg := testCfg(hostPort(srv), "readkey", "writekey")
			b, err := NewBackend("bunny", "", cfg)
			if err != nil {
				t.Fatalf("NewBackend: %v", err)
			}

			state, transient, err := b.Probe(context.Background(), sha)
			if err != nil && c.status < 500 {
				t.Fatalf("unexpected error: %v", err)
			}
			if state != c.wantState {
				t.Fatalf("status %d: expected state %v, got %v", c.status, c.wantState, state)
			}
			if transient != c.wantTransient {
				t.Fatalf("status %d: expected transient=%v, got %v", c.status, c.wantTransient, transient)
			}
			if f.headCount != 0 {
				t.Fatalf("expected zero HEAD requests, got %d", f.headCount)
			}
		})
	}
}

func TestBunnyPutSequence(t *testing.T) {
	t.Run("absent sha", func(t *testing.T) {
		sha := shaOf("new-blob")
		f := newFakeBunny()
		srv := httptest.NewServer(f.handler())
		defer srv.Close()

		cfg := testCfg(hostPort(srv), "readkey", "writekey")
		b, err := NewBackend("bunny", "", cfg)
		if err != nil {
			t.Fatalf("NewBackend: %v", err)
		}

		dir := t.TempDir()
		srcPath := filepath.Join(dir, "src")
		if err := os.WriteFile(srcPath, []byte("new-blob-content"), 0644); err != nil {
			t.Fatal(err)
		}

		if err := b.Put(context.Background(), sha, srcPath); err != nil {
			t.Fatalf("Put: %v", err)
		}

		reqs := f.requestsSnapshot()
		if len(reqs) != 2 {
			t.Fatalf("expected 2 requests (probe, put), got %d: %+v", len(reqs), reqs)
		}
		if reqs[0].Method != "GET" || reqs[0].Range != "bytes=0-0" {
			t.Fatalf("expected first request to be range probe GET, got %+v", reqs[0])
		}
		if reqs[1].Method != "PUT" {
			t.Fatalf("expected second request to be PUT, got %+v", reqs[1])
		}
		if got := reqs[1].Headers.Get("Checksum"); got != strings.ToUpper(sha) {
			t.Fatalf("expected Checksum %s, got %s", strings.ToUpper(sha), got)
		}
		if got := reqs[1].Headers.Get("AccessKey"); got != "writekey" {
			t.Fatalf("expected AccessKey writekey, got %s", got)
		}
		if f.headCount != 0 {
			t.Fatalf("expected zero HEAD requests, got %d", f.headCount)
		}
	})

	t.Run("present sha", func(t *testing.T) {
		sha := shaOf("existing-blob")
		f := newFakeBunny()
		f.blobs[sha] = []byte("existing-blob-content")
		srv := httptest.NewServer(f.handler())
		defer srv.Close()

		cfg := testCfg(hostPort(srv), "readkey", "writekey")
		b, err := NewBackend("bunny", "", cfg)
		if err != nil {
			t.Fatalf("NewBackend: %v", err)
		}

		dir := t.TempDir()
		srcPath := filepath.Join(dir, "src")
		if err := os.WriteFile(srcPath, []byte("existing-blob-content"), 0644); err != nil {
			t.Fatal(err)
		}

		if err := b.Put(context.Background(), sha, srcPath); err != nil {
			t.Fatalf("Put: %v", err)
		}

		reqs := f.requestsSnapshot()
		if len(reqs) != 1 {
			t.Fatalf("expected probe-only (1 request) since present, got %d: %+v", len(reqs), reqs)
		}
		if reqs[0].Method != "GET" {
			t.Fatalf("expected GET probe, got %+v", reqs[0])
		}
	})
}

func TestReadWriteKeySplit(t *testing.T) {
	sha := shaOf("split-blob")
	f := newFakeBunny()
	srv := httptest.NewServer(f.handler())
	defer srv.Close()

	cfg := testCfg(hostPort(srv), "readkeyXXX", "writekeyYYY")
	b, err := NewBackend("bunny", "", cfg)
	if err != nil {
		t.Fatalf("NewBackend: %v", err)
	}

	dir := t.TempDir()
	srcPath := filepath.Join(dir, "src")
	if err := os.WriteFile(srcPath, []byte("split-blob-content"), 0644); err != nil {
		t.Fatal(err)
	}

	if err := b.Put(context.Background(), sha, srcPath); err != nil {
		t.Fatalf("Put: %v", err)
	}

	reqs := f.requestsSnapshot()
	if len(reqs) != 2 {
		t.Fatalf("expected 2 requests, got %d", len(reqs))
	}
	if got := reqs[0].Headers.Get("AccessKey"); got != "readkeyXXX" {
		t.Fatalf("probe expected AccessKey readkeyXXX, got %s", got)
	}
	if got := reqs[1].Headers.Get("AccessKey"); got != "writekeyYYY" {
		t.Fatalf("put expected AccessKey writekeyYYY, got %s", got)
	}
	if reqs[0].Headers.Get("AccessKey") == reqs[1].Headers.Get("AccessKey") {
		t.Fatalf("expected distinct read/write keys")
	}
}

func TestBunnyNoReadKeyFailsClosed(t *testing.T) {
	// Grep-based tripwire: no non-test depot source may reference stdin/tty.
	dir := "."
	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatalf("ReadDir: %v", err)
	}
	for _, e := range entries {
		name := e.Name()
		if e.IsDir() || !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
			continue
		}
		data, err := os.ReadFile(filepath.Join(dir, name))
		if err != nil {
			t.Fatalf("ReadFile %s: %v", name, err)
		}
		s := string(data)
		if strings.Contains(s, "os.Stdin") || strings.Contains(s, "bufio.NewReader(os.Stdin)") || strings.Contains(s, "/dev/tty") {
			t.Fatalf("%s references stdin/tty; credential prompts are banned", name)
		}
	}

	// Confirm undrained pipe: swap in an os.Pipe as stdin-equivalent to prove
	// no read occurs.
	r, w, err := os.Pipe()
	if err != nil {
		t.Fatalf("Pipe: %v", err)
	}
	oldStdin := os.Stdin
	os.Stdin = r
	defer func() { os.Stdin = oldStdin; r.Close() }()

	cfg := testCfg("storage.example.com", "", "writekey")
	_, err = NewBackend("bunny", "", cfg)
	if err == nil {
		t.Fatal("expected error for empty ReadKey")
	}
	if !strings.Contains(err.Error(), "ReadKey") && !strings.Contains(err.Error(), "BUNNY_STORAGE_READ_PASSWORD") && !strings.Contains(err.Error(), "BUNNY_STORAGE_PASSWORD") {
		t.Fatalf("expected error to mention missing env var, got: %v", err)
	}

	w.Close()
	// If code read from stdin it would have blocked already (pipe with no
	// writer-side data yet); assert the pipe is still open/undrained by
	// writing now and reading it back ourselves.
	if _, err := w.Write([]byte("x")); err == nil {
		t.Fatal("expected write to closed pipe writer to fail")
	}
}

func TestBunnyNoStorageHostFailsClosed(t *testing.T) {
	cfg := testCfg("", "readkey", "writekey")
	_, err := NewBackend("bunny", "", cfg)
	if err == nil {
		t.Fatal("expected error for empty StorageHost")
	}
	if !strings.Contains(err.Error(), "StorageHost") && !strings.Contains(err.Error(), "BUNNY_STORAGE_HOST") {
		t.Fatalf("expected error to mention missing StorageHost/BUNNY_STORAGE_HOST, got: %v", err)
	}
}

func TestGetHashMismatchDeletes(t *testing.T) {
	sha := shaOf("get-mismatch-blob")
	f := newFakeBunny()
	f.blobs[sha] = []byte("wrong content")
	srv := httptest.NewServer(f.handler())
	defer srv.Close()

	cfg := testCfg(hostPort(srv), "readkey", "writekey")
	// force CDN unreachable so Get falls back to storage
	cfg.CDNBase = "http://127.0.0.1:1"
	b, err := NewBackend("bunny", "", cfg)
	if err != nil {
		t.Fatalf("NewBackend: %v", err)
	}

	dir := t.TempDir()
	dest := filepath.Join(dir, "dest")

	err = b.Get(context.Background(), sha, dest)
	if err == nil {
		t.Fatal("expected hash mismatch error")
	}
	if _, statErr := os.Stat(dest); !os.IsNotExist(statErr) {
		t.Fatalf("expected dest to be removed on mismatch, stat err: %v", statErr)
	}
}

func TestCDNPutReadOnly(t *testing.T) {
	cfg := testCfg("storage.example.com", "readkey", "writekey")
	b, err := NewBackend("cdn", "", cfg)
	if err != nil {
		t.Fatalf("NewBackend: %v", err)
	}

	dir := t.TempDir()
	srcPath := filepath.Join(dir, "src")
	if err := os.WriteFile(srcPath, []byte("data"), 0644); err != nil {
		t.Fatal(err)
	}

	err = b.Put(context.Background(), shaOf("anything"), srcPath)
	if err == nil {
		t.Fatal("expected error for cdn Put (read-only)")
	}
	if !strings.Contains(err.Error(), "read-only") {
		t.Fatalf("expected read-only error, got: %v", err)
	}
}

// TestNoHeadInSources is the anti-HEAD regression tripwire from field note 3:
// grep-assert no http.MethodHead/.Head( usage in non-test depot sources.
func TestNoHeadInSources(t *testing.T) {
	dir := "."
	entries, err := os.ReadDir(dir)
	if err != nil {
		t.Fatalf("ReadDir: %v", err)
	}
	for _, e := range entries {
		name := e.Name()
		if e.IsDir() || !strings.HasSuffix(name, ".go") || strings.HasSuffix(name, "_test.go") {
			continue
		}
		data, err := os.ReadFile(filepath.Join(dir, name))
		if err != nil {
			t.Fatalf("ReadFile %s: %v", name, err)
		}
		s := string(data)
		if strings.Contains(s, "http.MethodHead") || strings.Contains(s, ".Head(") {
			t.Fatalf("%s references HEAD probe (banned)", name)
		}
	}
}

// TestLocalBackendViaFactory sanity-checks NewBackend("local", ...).
func TestLocalBackendViaFactory(t *testing.T) {
	root := t.TempDir()
	b, err := NewBackend("local", root, Config{})
	if err != nil {
		t.Fatalf("NewBackend: %v", err)
	}
	lb, ok := b.(*LocalBackend)
	if !ok {
		t.Fatalf("expected *LocalBackend, got %T", b)
	}
	if lb.Root != root {
		t.Fatalf("expected Root=%s, got %s", root, lb.Root)
	}

	if _, err := NewBackend("local", "", Config{}); err == nil {
		t.Fatal("expected error for empty local root")
	}

	if _, err := NewBackend("nonsense", "", Config{}); err == nil {
		t.Fatal("expected error for unknown backend name")
	}
}