package signature_test

import (
	"errors"
	"strings"
	"testing"
	"time"

	"sneak.berlin/go/pixa/internal/signature"
)

// Shared fixture values used across the signature tests.
const (
	testHost       = "cdn.example.com"
	testPath       = "/photos/cat.jpg"
	testFormatWebP = "webp"
	testFormatPNG  = "png"
	testSignedPath = "/v1/image/cdn.example.com/photos/cat.jpg/800x600.webp"
	testSig        = "abc123"
)

func TestSigner_Sign(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key")

	req := &signature.Request{
		SourceHost:  testHost,
		SourcePath:  testPath,
		SourceQuery: "",
		Width:       800,
		Height:      600,
		Format:      testFormatWebP,
		Expires:     time.Unix(1704067200, 0), // Fixed timestamp for reproducibility
	}

	sig1 := signer.Sign(req)
	sig2 := signer.Sign(req)

	// Same input should produce same signature
	if sig1 != sig2 {
		t.Errorf("Sign() produced different signatures for same input: %q vs %q",
			sig1, sig2)
	}

	// Signature should be non-empty
	if sig1 == "" {
		t.Error("Sign() produced empty signature")
	}

	// Different input should produce different signature
	req2 := &signature.Request{
		SourceHost:  testHost,
		SourcePath:  "/photos/dog.jpg", // Different path
		SourceQuery: "",
		Width:       800,
		Height:      600,
		Format:      testFormatWebP,
		Expires:     time.Unix(1704067200, 0),
	}

	sig3 := signer.Sign(req2)
	if sig1 == sig3 {
		t.Error("Sign() produced same signature for different input")
	}
}

// validVerifyRequest returns a fully-populated request that verifies
// successfully once signed.
func validVerifyRequest() *signature.Request {
	return &signature.Request{
		SourceHost: testHost,
		SourcePath: testPath,
		Width:      800,
		Height:     600,
		Format:     testFormatWebP,
		Expires:    time.Now().Add(1 * time.Hour),
	}
}

type verifyCase struct {
	name    string
	setup   func() *signature.Request
	wantErr error
}

func verifyCases(signer *signature.Signer) []verifyCase {
	return []verifyCase{
		{
			name: "valid signature",
			setup: func() *signature.Request {
				req := validVerifyRequest()
				req.Signature = signer.Sign(req)

				return req
			},
			wantErr: nil,
		},
		{
			name: "expired signature",
			setup: func() *signature.Request {
				req := validVerifyRequest()
				req.Expires = time.Now().Add(-1 * time.Hour)
				req.Signature = signer.Sign(req)

				return req
			},
			wantErr: signature.ErrExpired,
		},
		{
			name: "invalid signature",
			setup: func() *signature.Request {
				req := validVerifyRequest()
				req.Signature = "invalid-signature"

				return req
			},
			wantErr: signature.ErrInvalid,
		},
		{
			name: "missing expiration",
			setup: func() *signature.Request {
				req := validVerifyRequest()
				req.Expires = time.Time{}
				req.Signature = "some-signature"

				return req
			},
			wantErr: signature.ErrMissingExpiration,
		},
		{
			name: "tampered request",
			setup: func() *signature.Request {
				req := validVerifyRequest()
				req.Signature = signer.Sign(req)
				req.SourcePath = "/photos/secret.jpg"

				return req
			},
			wantErr: signature.ErrInvalid,
		},
	}
}

func TestSigner_Verify(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key")

	for _, tt := range verifyCases(signer) {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			req := tt.setup()
			err := signer.Verify(req)

			if tt.wantErr == nil {
				if err != nil {
					t.Errorf("Verify() unexpected error = %v", err)
				}

				return
			}

			if !errors.Is(err, tt.wantErr) {
				t.Errorf("Verify() error = %v, wantErr %v", err, tt.wantErr)
			}
		})
	}
}

type tamperCase struct {
	name   string
	tamper func(r *signature.Request)
}

// exactMatchTamperCases mutates one signed component per case; every
// mutation must cause verification to fail with ErrInvalid.
func exactMatchTamperCases() []tamperCase {
	return []tamperCase{
		{
			name:   "parent domain does not match subdomain",
			tamper: func(r *signature.Request) { r.SourceHost = "example.com" },
		},
		{
			name:   "subdomain does not match parent domain",
			tamper: func(r *signature.Request) { r.SourceHost = "images.cdn.example.com" },
		},
		{
			name:   "sibling subdomain does not match",
			tamper: func(r *signature.Request) { r.SourceHost = "images.example.com" },
		},
		{
			name:   "host with suffix appended does not match",
			tamper: func(r *signature.Request) { r.SourceHost = testHost + ".evil.com" },
		},
		{
			name:   "host with prefix does not match",
			tamper: func(r *signature.Request) { r.SourceHost = "evilcdn.example.com" },
		},
		{
			name:   "different path does not match",
			tamper: func(r *signature.Request) { r.SourcePath = "/photos/dog.jpg" },
		},
		{
			name:   "path suffix does not match",
			tamper: func(r *signature.Request) { r.SourcePath = testPath + "/extra" },
		},
		{
			name:   "path prefix does not match",
			tamper: func(r *signature.Request) { r.SourcePath = "/other" + testPath },
		},
		{
			name:   "different query does not match",
			tamper: func(r *signature.Request) { r.SourceQuery = "token=xyz" },
		},
		{
			name:   "added query does not match empty query",
			tamper: func(r *signature.Request) { r.SourceQuery = "extra=1" },
		},
		{
			name:   "removed query does not match",
			tamper: func(r *signature.Request) { r.SourceQuery = "" },
		},
		{
			name:   "different width does not match",
			tamper: func(r *signature.Request) { r.Width = 801 },
		},
		{
			name:   "different height does not match",
			tamper: func(r *signature.Request) { r.Height = 601 },
		},
		{
			name:   "different format does not match",
			tamper: func(r *signature.Request) { r.Format = testFormatPNG },
		},
	}
}

// TestSigner_Verify_ExactMatchOnly verifies that signatures enforce exact
// matching on every URL component. No suffix matching, wildcard matching,
// or partial matching is supported.
func TestSigner_Verify_ExactMatchOnly(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key")

	// Base request that we'll sign, then tamper with individual fields.
	baseReq := func() *signature.Request {
		req := &signature.Request{
			SourceHost:  testHost,
			SourcePath:  testPath,
			SourceQuery: "token=abc",
			Width:       800,
			Height:      600,
			Format:      testFormatWebP,
			Expires:     time.Now().Add(1 * time.Hour),
		}
		req.Signature = signer.Sign(req)

		return req
	}

	for _, tt := range exactMatchTamperCases() {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			req := baseReq()
			tt.tamper(req)

			err := signer.Verify(req)
			if !errors.Is(err, signature.ErrInvalid) {
				t.Errorf("Verify() = %v, want %v", err, signature.ErrInvalid)
			}
		})
	}

	// Verify the unmodified base request still passes
	t.Run("unmodified request passes", func(t *testing.T) {
		t.Parallel()

		req := baseReq()

		err := signer.Verify(req)
		if err != nil {
			t.Errorf("Verify() unmodified request failed: %v", err)
		}
	})
}

// TestSigner_Sign_ExactHostInData verifies that Sign uses the exact host
// string in the signature data, producing different signatures for
// suffix-related hosts.
func TestSigner_Sign_ExactHostInData(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key")

	hosts := []string{
		testHost,
		"example.com",
		"images.example.com",
		"images.cdn.example.com",
		"cdn.example.com.evil.com",
	}

	sigs := make(map[string]string)

	for _, host := range hosts {
		req := &signature.Request{
			SourceHost:  host,
			SourcePath:  testPath,
			SourceQuery: "",
			Width:       800,
			Height:      600,
			Format:      testFormatWebP,
			Expires:     time.Unix(1704067200, 0),
		}

		sig := signer.Sign(req)
		if existing, ok := sigs[sig]; ok {
			t.Errorf("hosts %q and %q produced the same signature", existing, host)
		}

		sigs[sig] = host
	}
}

func TestSigner_DifferentKeys(t *testing.T) {
	t.Parallel()

	signer1 := signature.New("secret-key-1")
	signer2 := signature.New("secret-key-2")

	req := &signature.Request{
		SourceHost: testHost,
		SourcePath: testPath,
		Width:      800,
		Height:     600,
		Format:     testFormatWebP,
		Expires:    time.Now().Add(1 * time.Hour),
	}

	// Sign with key 1
	req.Signature = signer1.Sign(req)

	// Verify with key 1 should succeed
	err := signer1.Verify(req)
	if err != nil {
		t.Errorf("Verify() with same key failed: %v", err)
	}

	// Verify with key 2 should fail
	err = signer2.Verify(req)
	if !errors.Is(err, signature.ErrInvalid) {
		t.Errorf("Verify() with different key should fail, got: %v", err)
	}
}

func TestGenerateSignedURL(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key")

	req := &signature.Request{
		SourceHost:  testHost,
		SourcePath:  testPath,
		SourceQuery: "",
		Width:       800,
		Height:      600,
		Format:      testFormatWebP,
	}

	ttl := 1 * time.Hour
	path, sig, exp := signer.GenerateSignedURL(req, ttl)

	// Path should be correct format
	if path != testSignedPath {
		t.Errorf("GenerateSignedURL() path = %q, want %q", path, testSignedPath)
	}

	// Signature should be non-empty
	if sig == "" {
		t.Error("GenerateSignedURL() produced empty signature")
	}

	// Expiration should be approximately now + TTL
	expTime := time.Unix(exp, 0)

	expectedExp := time.Now().Add(ttl)
	if expTime.Sub(expectedExp) > time.Second {
		t.Errorf("GenerateSignedURL() exp time off by too much")
	}

	// Request should have been updated with signature and expiration
	if req.Signature != sig {
		t.Errorf("GenerateSignedURL() didn't update request signature")
	}
}

func TestGenerateSignedURL_OrigSize(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key")

	req := &signature.Request{
		SourceHost: testHost,
		SourcePath: testPath,
		Width:      0, // Original size
		Height:     0,
		Format:     testFormatPNG,
	}

	path, _, _ := signer.GenerateSignedURL(req, time.Hour)

	expectedPath := "/v1/image/cdn.example.com/photos/cat.jpg/orig.png"
	if path != expectedPath {
		t.Errorf("GenerateSignedURL() path = %q, want %q", path, expectedPath)
	}
}

func TestGenerateSignedURL_WithQueryString(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key-for-testing!")

	req := &signature.Request{
		SourceHost:  testHost,
		SourcePath:  testPath,
		SourceQuery: "token=abc&v=2",
		Width:       800,
		Height:      600,
		Format:      testFormatWebP,
	}

	path, _, _ := signer.GenerateSignedURL(req, time.Hour)

	// The path must NOT contain a bare "?" that would be interpreted as
	// a query string delimiter. The size segment must appear as the last
	// path component.
	if strings.Contains(path, "?token=abc") {
		t.Errorf("GenerateSignedURL() produced bare query string in path: %q", path)
	}

	// The size segment must be present in the path
	if !strings.Contains(path, "/800x600.webp") {
		t.Errorf("GenerateSignedURL() missing size segment in path: %q", path)
	}

	// Path should end with the size.format, not with query params
	if !strings.HasSuffix(path, "/800x600.webp") {
		t.Errorf("GenerateSignedURL() path should end with size.format: %q", path)
	}
}

func TestGenerateSignedURL_WithoutQueryString(t *testing.T) {
	t.Parallel()

	signer := signature.New("test-secret-key-for-testing!")

	req := &signature.Request{
		SourceHost: testHost,
		SourcePath: testPath,
		Width:      800,
		Height:     600,
		Format:     testFormatWebP,
	}

	path, _, _ := signer.GenerateSignedURL(req, time.Hour)

	if path != testSignedPath {
		t.Errorf("GenerateSignedURL() path = %q, want %q", path, testSignedPath)
	}
}

func TestParseParams(t *testing.T) {
	t.Parallel()

	tests := []struct {
		name      string
		sig       string
		expStr    string
		wantSig   string
		wantErr   bool
		checkTime bool
	}{
		{
			name:    "valid params",
			sig:     testSig,
			expStr:  "1704067200",
			wantSig: testSig,
			wantErr: false,
		},
		{
			name:    "empty expiration",
			sig:     testSig,
			expStr:  "",
			wantSig: testSig,
			wantErr: false,
		},
		{
			name:    "invalid expiration",
			sig:     testSig,
			expStr:  "not-a-number",
			wantErr: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			t.Parallel()

			sig, exp, err := signature.ParseParams(tt.sig, tt.expStr)

			if tt.wantErr {
				if err == nil {
					t.Error("ParseParams() expected error, got nil")
				}

				return
			}

			if err != nil {
				t.Errorf("ParseParams() unexpected error = %v", err)

				return
			}

			if sig != tt.wantSig {
				t.Errorf("sig = %q, want %q", sig, tt.wantSig)
			}

			if tt.expStr != "" && exp.IsZero() {
				t.Error("exp should not be zero when expStr is provided")
			}
		})
	}
}