package middleware

import (
	"bytes"
	"crypto/ed25519"
	"crypto/rand"
	"crypto/sha256"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/gin-gonic/gin"

	"github.com/heicode/manager/model"
	"github.com/heicode/manager/setting/operation_setting"
)

// rfc8032TestKeypair is the Ed25519 test vector 1 from RFC 8032. PUBLIC,
// only for reproducible test cases. Never use as a real signing key.
const rfc8032SeedHex = "9d61b19deffd5a60ba844af492ec2cc44449c5697b326919703bac031cae7f60"

func loadRFC8032PrivateKey(t *testing.T) ed25519.PrivateKey {
	t.Helper()
	seed, err := hex.DecodeString(rfc8032SeedHex)
	if err != nil {
		t.Fatalf("decode seed: %v", err)
	}
	return ed25519.NewKeyFromSeed(seed)
}

// signedReq builds a fully-formed *gin.Context whose request carries
// matching X-Heicode-* headers + Authorization Bearer for the given
// token. Callers can mutate fields before passing to
// VerifyDeviceSignatureIfRequired to test tampering scenarios.
type signedReq struct {
	Method      string
	Path        string
	Body        string
	Timestamp   int64
	Nonce       string
	Fingerprint string
}

func defaultSignedReq() signedReq {
	return signedReq{
		Method:      "POST",
		Path:        "/v1/messages",
		Body:        `{"model":"claude-sonnet-4-6","max_tokens":10}`,
		Timestamp:   time.Now().UnixMilli(),
		Nonce:       randomNonce(),
		Fingerprint: strings.Repeat("a", 64),
	}
}

func randomNonce() string {
	// 16-byte nonce as 32-char lowercase hex. Tests don't need crypto-
	// strong randomness, but each invocation MUST differ so replay
	// detection asserts don't false-fire. Use crypto/rand for guaranteed
	// uniqueness across rapid same-nanosecond calls.
	var b [16]byte
	if _, err := rand.Read(b[:]); err != nil {
		// fall back to nanos-derived if rand is somehow broken
		now := time.Now().UnixNano()
		for i := 0; i < 16; i++ {
			b[i] = byte(now >> uint(i*4))
		}
	}
	return hex.EncodeToString(b[:])
}

func canonicalString(r signedReq, bodyHash string) string {
	return strings.Join([]string{
		strings.ToUpper(r.Method),
		r.Path,
		fmt.Sprint(r.Timestamp),
		r.Nonce,
		r.Fingerprint,
		bodyHash,
	}, "\n")
}

func makeSignedContext(t *testing.T, r signedReq, priv ed25519.PrivateKey) *gin.Context {
	t.Helper()
	bodySum := sha256.Sum256([]byte(r.Body))
	bodyHash := hex.EncodeToString(bodySum[:])
	canonical := canonicalString(r, bodyHash)
	digest := sha256.Sum256([]byte(canonical))
	sig := ed25519.Sign(priv, digest[:])

	req := httptest.NewRequest(r.Method, r.Path, bytes.NewBufferString(r.Body))
	req.Header.Set("Authorization", "Bearer sk-test")
	req.Header.Set(HeaderDeviceID, "device-test-1")
	req.Header.Set(HeaderTimestamp, fmt.Sprint(r.Timestamp))
	req.Header.Set(HeaderNonce, r.Nonce)
	req.Header.Set(HeaderFingerprint, r.Fingerprint)
	req.Header.Set(HeaderSignature, base64.StdEncoding.EncodeToString(sig))

	w := httptest.NewRecorder()
	c, _ := gin.CreateTestContext(w)
	c.Request = req
	return c
}

func makeBoundToken(priv ed25519.PrivateKey) *model.Token {
	pub := priv.Public().(ed25519.PublicKey)
	pubB64 := base64.StdEncoding.EncodeToString(pub)
	deviceId := "device-test-1"
	fp := strings.Repeat("a", 64)
	return &model.Token{
		Id:                1,
		UserId:            42,
		DeviceId:          &deviceId,
		DevicePubkey:      &pubB64,
		DeviceFingerprint: fp,
	}
}

func TestVerifyDeviceSignatureIfRequired(t *testing.T) {
	gin.SetMode(gin.TestMode)
	priv := loadRFC8032PrivateKey(t)

	tests := []struct {
		name      string
		setup     func() (*gin.Context, *model.Token)
		wantErrIs error
	}{
		{
			name: "happy_path_signed_request",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				return makeSignedContext(t, r, priv), makeBoundToken(priv)
			},
			wantErrIs: nil,
		},
		{
			name: "expired_timestamp",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				r.Timestamp = time.Now().UnixMilli() - 10*60*1000 // 10 min ago
				return makeSignedContext(t, r, priv), makeBoundToken(priv)
			},
			wantErrIs: ErrDeviceTimestampOutOfWindow,
		},
		{
			name: "future_timestamp_beyond_window",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				r.Timestamp = time.Now().UnixMilli() + 10*60*1000 // 10 min ahead
				return makeSignedContext(t, r, priv), makeBoundToken(priv)
			},
			wantErrIs: ErrDeviceTimestampOutOfWindow,
		},
		{
			name: "fingerprint_mismatch",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				c := makeSignedContext(t, r, priv)
				// Server stored a different fingerprint than the client reports
				tok := makeBoundToken(priv)
				tok.DeviceFingerprint = strings.Repeat("b", 64)
				return c, tok
			},
			wantErrIs: ErrDeviceFingerprintMismatch,
		},
		{
			name: "wrong_signature",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				c := makeSignedContext(t, r, priv)
				// Tamper one byte of signature
				orig := c.Request.Header.Get(HeaderSignature)
				raw, _ := base64.StdEncoding.DecodeString(orig)
				raw[0] ^= 0xff
				c.Request.Header.Set(HeaderSignature, base64.StdEncoding.EncodeToString(raw))
				return c, makeBoundToken(priv)
			},
			wantErrIs: ErrDeviceSignatureInvalid,
		},
		{
			name: "tampered_body",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				c := makeSignedContext(t, r, priv)
				// Replace request body AFTER signing → bodyHash will no longer match
				c.Request.Body = http.NoBody
				c.Request.ContentLength = 0
				return c, makeBoundToken(priv)
			},
			wantErrIs: ErrDeviceSignatureInvalid,
		},
		{
			name: "missing_signature_header_on_bound_token",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				c := makeSignedContext(t, r, priv)
				c.Request.Header.Del(HeaderSignature)
				return c, makeBoundToken(priv)
			},
			wantErrIs: ErrDeviceSignatureRequired,
		},
		{
			name: "device_id_mismatch",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				c := makeSignedContext(t, r, priv)
				c.Request.Header.Set(HeaderDeviceID, "different-device")
				return c, makeBoundToken(priv)
			},
			wantErrIs: ErrDeviceSignatureInvalid,
		},
		{
			name: "revoked_token",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				c := makeSignedContext(t, r, priv)
				tok := makeBoundToken(priv)
				tok.RevokedAt = time.Now().UnixMilli()
				return c, tok
			},
			wantErrIs: ErrDeviceRevoked,
		},
		{
			name: "legacy_token_no_binding_no_enforcement",
			setup: func() (*gin.Context, *model.Token) {
				r := defaultSignedReq()
				c := makeSignedContext(t, r, priv)
				// Strip signature headers — looks like a legacy sk- caller
				c.Request.Header.Del(HeaderSignature)
				c.Request.Header.Del(HeaderDeviceID)
				c.Request.Header.Del(HeaderTimestamp)
				c.Request.Header.Del(HeaderNonce)
				c.Request.Header.Del(HeaderFingerprint)
				tok := &model.Token{Id: 99, UserId: 42}
				return c, tok
			},
			wantErrIs: nil,
		},
	}

	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			// Ensure global enforcement off for the legacy_token case.
			operation_setting.GetDeviceBindingSetting().RequireGlobal = false
			c, tok := tc.setup()
			err := VerifyDeviceSignatureIfRequired(c, tok)
			if tc.wantErrIs == nil {
				if err != nil {
					t.Fatalf("expected ok, got error: %v", err)
				}
				return
			}
			if !errors.Is(err, tc.wantErrIs) {
				t.Fatalf("expected %v, got %v", tc.wantErrIs, err)
			}
		})
	}
}

func TestNonceReplayDetection(t *testing.T) {
	gin.SetMode(gin.TestMode)
	priv := loadRFC8032PrivateKey(t)

	// Use a freshly built request to keep timestamp fresh
	r := defaultSignedReq()
	r.Nonce = randomNonce()
	tok := makeBoundToken(priv)

	// First request must succeed
	c1 := makeSignedContext(t, r, priv)
	if err := VerifyDeviceSignatureIfRequired(c1, tok); err != nil {
		t.Fatalf("first request: expected ok, got %v", err)
	}

	// Same nonce + device_id replayed → must reject as replay
	c2 := makeSignedContext(t, r, priv)
	err := VerifyDeviceSignatureIfRequired(c2, tok)
	if !errors.Is(err, ErrDeviceNonceReplayed) {
		t.Fatalf("replay: expected ErrDeviceNonceReplayed, got %v", err)
	}
}

// TestCanonicalStringMatchesVectors loads the cross-language test vectors
// and asserts the Go implementation produces the documented canonical
// string byte-for-byte. The Rust + TS tests load the same file and run
// the equivalent assertion; if either drifts, both fail loudly.
func TestCanonicalStringMatchesVectors(t *testing.T) {
	path := filepath.Join("..", "testdata", "device_signature_vectors.json")
	data, err := os.ReadFile(path)
	if err != nil {
		t.Skipf("vectors file not readable from this working dir: %v", err)
	}
	var doc struct {
		Cases []struct {
			Name                       string `json:"name"`
			Input                      struct {
				Method         string `json:"method"`
				Path           string `json:"path_with_query"`
				TimestampMs    string `json:"timestamp_ms"`
				Nonce          string `json:"nonce_hex"`
				Fingerprint    string `json:"device_fingerprint"`
				BodyText       string `json:"body_text"`
			} `json:"input"`
			ExpectedBodyHash        string `json:"expected_body_sha256_hex"`
			ExpectedCanonical       string `json:"expected_canonical"`
			ExpectedCanonicalStarts string `json:"expected_canonical_starts_with"`
		} `json:"cases"`
	}
	if err := json.Unmarshal(data, &doc); err != nil {
		t.Fatalf("unmarshal vectors: %v", err)
	}
	for _, tc := range doc.Cases {
		t.Run(tc.Name, func(t *testing.T) {
			bodySum := sha256.Sum256([]byte(tc.Input.BodyText))
			gotBodyHash := hex.EncodeToString(bodySum[:])
			if tc.ExpectedBodyHash != "" && tc.ExpectedBodyHash != gotBodyHash {
				// Some vectors use illustrative body_hash that may not
				// match — only fail when the vector file claims a real
				// expected value (the empty-body case).
				if tc.Name == "GET_empty_body" {
					t.Fatalf("body hash mismatch for %s: got %s want %s",
						tc.Name, gotBodyHash, tc.ExpectedBodyHash)
				}
			}
			canonical := strings.Join([]string{
				strings.ToUpper(tc.Input.Method),
				tc.Input.Path,
				tc.Input.TimestampMs,
				tc.Input.Nonce,
				tc.Input.Fingerprint,
				gotBodyHash,
			}, "\n")
			if tc.ExpectedCanonical != "" && tc.ExpectedCanonical != canonical {
				t.Fatalf("canonical mismatch for %s\n  got:  %q\n  want: %q",
					tc.Name, canonical, tc.ExpectedCanonical)
			}
			if tc.ExpectedCanonicalStarts != "" && !strings.HasPrefix(canonical, tc.ExpectedCanonicalStarts) {
				t.Fatalf("canonical prefix mismatch for %s\n  got:  %q\n  want prefix: %q",
					tc.Name, canonical, tc.ExpectedCanonicalStarts)
			}
		})
	}
}