package main_test

import (
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
	"syscall"
	"testing"
	"time"
)

// TestE2E_FullOAuthAndMCPFlow exercises every wired component end-to-end:
//
//   1. Build the broker binary (already done in TestMain).
//   2. Build forgejo-mcp from sibling source so the broker can spawn it.
//   3. Stand up a fake Forgejo (httptest.Server) covering the OAuth and
//      OIDC endpoints plus the API surface forgejo-mcp probes at startup.
//   4. Run the broker with all that wired up.
//   5. Walk through: register → authorize → callback → token →
//      /mcp (initialize via Bearer token) → tools/list.
//
// Skipped under -short and when the sibling forgejo-mcp source isn't
// present. This test is the closest local stand-in for the manual
// Claude.ai validation in docs/phase7-findings.md.
func TestE2E_FullOAuthAndMCPFlow(t *testing.T) {
	if testing.Short() {
		t.Skip("end-to-end test (~5s); rerun without -short")
	}

	forgejoMCPBin := buildForgejoMCPSibling(t)
	fakeForgejo := startFakeForgejo(t)
	storePath := filepath.Join(t.TempDir(), "broker.db")
	listenAddr := freePort(t)
	publicURL := "http://" + listenAddr

	cmd := exec.Command(binPath,
		"--public-url", publicURL,
		"--forgejo-url", fakeForgejo.URL,
		"--forgejo-oauth-client-id", "broker-app",
		"--forgejo-oauth-client-secret", "broker-secret",
		"--forgejo-mcp-binary", forgejoMCPBin,
		"--listen", listenAddr,
		"--store-path", storePath,
		"--debug",
	)
	cmd.Env = []string{"PATH=" + os.Getenv("PATH")}
	stderr := &captureBuffer{}
	cmd.Stderr = stderr
	if err := cmd.Start(); err != nil {
		t.Fatalf("start broker: %v", err)
	}
	defer func() {
		if cmd.Process != nil {
			_ = cmd.Process.Signal(syscall.SIGTERM)
			_, _ = cmd.Process.Wait()
		}
	}()
	waitListening(t, listenAddr, 5*time.Second)

	// Step 1 — register a client.
	clientID := registerClient(t, publicURL, "https://app.example.com/cb")

	// Step 2 — authorize. We use a no-redirect HTTP client so we can
	// inspect the redirect Location and pick out the Forgejo state.
	verifier := "a-pkce-verifier-thats-quite-long-12345678"
	challenge := pkceChallenge(verifier)
	authQ := url.Values{
		"response_type":         {"code"},
		"client_id":             {clientID},
		"redirect_uri":          {"https://app.example.com/cb"},
		"state":                 {"client-csrf"},
		"code_challenge":        {challenge},
		"code_challenge_method": {"S256"},
	}
	resp := getNoRedirect(t, publicURL+"/oauth/authorize?"+authQ.Encode())
	resp.Body.Close()
	if resp.StatusCode != http.StatusFound {
		t.Fatalf("authorize: status = %d, want 302", resp.StatusCode)
	}
	upstream, err := url.Parse(resp.Header.Get("Location"))
	if err != nil {
		t.Fatalf("parse Location: %v", err)
	}
	forgejoState := upstream.Query().Get("state")
	if forgejoState == "" {
		t.Fatalf("authorize did not produce a Forgejo state: %s", upstream)
	}

	// Step 3 — fake Forgejo would have authenticated the user and
	// redirected to /oauth/callback. Simulate that.
	cb := getNoRedirect(t, publicURL+"/oauth/callback?code=upstream-code&state="+forgejoState)
	cb.Body.Close()
	if cb.StatusCode != http.StatusFound {
		t.Fatalf("callback: status = %d, want 302", cb.StatusCode)
	}
	cbLoc, _ := url.Parse(cb.Header.Get("Location"))
	brokerCode := cbLoc.Query().Get("code")
	if brokerCode == "" {
		t.Fatalf("callback did not return broker code: %s", cbLoc)
	}

	// Step 4 — exchange broker code for access + refresh tokens.
	tokForm := url.Values{
		"grant_type":    {"authorization_code"},
		"code":          {brokerCode},
		"client_id":     {clientID},
		"redirect_uri":  {"https://app.example.com/cb"},
		"code_verifier": {verifier},
	}
	tokResp, err := http.PostForm(publicURL+"/oauth/token", tokForm)
	if err != nil {
		t.Fatalf("token: %v", err)
	}
	defer tokResp.Body.Close()
	if tokResp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(tokResp.Body)
		t.Fatalf("token status = %d: %s", tokResp.StatusCode, body)
	}
	var tokens struct {
		AccessToken string `json:"access_token"`
	}
	if err := json.NewDecoder(tokResp.Body).Decode(&tokens); err != nil {
		t.Fatalf("decode token: %v", err)
	}
	if tokens.AccessToken == "" {
		t.Fatalf("token response missing access_token")
	}

	// Step 5 — call /mcp with the bearer token. First the MCP `initialize`
	// handshake; the broker spawns a forgejo-mcp child for this session.
	initBody := `{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"e2e","version":"1"}}}`
	initReq, _ := http.NewRequest(http.MethodPost, publicURL+"/mcp", strings.NewReader(initBody))
	initReq.Header.Set("Authorization", "Bearer "+tokens.AccessToken)
	initReq.Header.Set("Content-Type", "application/json")
	initResp, err := http.DefaultClient.Do(initReq)
	if err != nil {
		t.Fatalf("initialize: %v", err)
	}
	defer initResp.Body.Close()
	if initResp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(initResp.Body)
		t.Fatalf("initialize status = %d: %s\n\nbroker stderr:\n%s", initResp.StatusCode, body, stderr.String())
	}
	sid := initResp.Header.Get("Mcp-Session-Id")
	if sid == "" {
		t.Fatalf("initialize did not return Mcp-Session-Id")
	}
	body, _ := io.ReadAll(initResp.Body)
	if !strings.Contains(string(body), `"protocolVersion"`) {
		t.Errorf("initialize response missing protocolVersion: %s", body)
	}

	// Step 6 — tools/list with the same sid. Different RPC, same forgejo-mcp child.
	listBody := `{"jsonrpc":"2.0","id":2,"method":"tools/list"}`
	listReq, _ := http.NewRequest(http.MethodPost, publicURL+"/mcp", strings.NewReader(listBody))
	listReq.Header.Set("Authorization", "Bearer "+tokens.AccessToken)
	listReq.Header.Set("Content-Type", "application/json")
	listReq.Header.Set("Mcp-Session-Id", sid)
	listResp, err := http.DefaultClient.Do(listReq)
	if err != nil {
		t.Fatalf("tools/list: %v", err)
	}
	defer listResp.Body.Close()
	listBytes, _ := io.ReadAll(listResp.Body)
	if listResp.StatusCode != http.StatusOK {
		t.Fatalf("tools/list status = %d: %s\n\nbroker stderr:\n%s",
			listResp.StatusCode, listBytes, stderr.String())
	}
	if !strings.Contains(string(listBytes), "get_forgejo_mcp_server_version") {
		t.Errorf("tools/list missing expected tool. Body: %s", listBytes)
	}

	// Step 7 — discovery surface returns issuer-rooted URLs derived from
	// --public-url, not from the test server's address.
	disc, err := http.Get(publicURL + "/.well-known/oauth-authorization-server")
	if err != nil {
		t.Fatalf("discovery: %v", err)
	}
	defer disc.Body.Close()
	var md map[string]any
	if err := json.NewDecoder(disc.Body).Decode(&md); err != nil {
		t.Fatalf("decode discovery: %v", err)
	}
	if md["issuer"] != publicURL {
		t.Errorf("issuer = %v, want %s", md["issuer"], publicURL)
	}
}

// captureBuffer is a thread-safe buffer for collecting child stderr.
type captureBuffer struct {
	mu  sync.Mutex
	buf strings.Builder
}

func (c *captureBuffer) Write(p []byte) (int, error) {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.buf.Write(p)
}

func (c *captureBuffer) String() string {
	c.mu.Lock()
	defer c.mu.Unlock()
	return c.buf.String()
}

func registerClient(t *testing.T, baseURL, redirectURI string) string {
	t.Helper()
	body, _ := json.Marshal(map[string]any{
		"redirect_uris": []string{redirectURI},
		"client_name":   "e2e-test",
	})
	resp, err := http.Post(baseURL+"/oauth/register", "application/json", strings.NewReader(string(body)))
	if err != nil {
		t.Fatalf("register: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusCreated {
		b, _ := io.ReadAll(resp.Body)
		t.Fatalf("register status = %d: %s", resp.StatusCode, b)
	}
	var r struct {
		ClientID string `json:"client_id"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&r); err != nil {
		t.Fatalf("decode register: %v", err)
	}
	return r.ClientID
}

func pkceChallenge(verifier string) string {
	sum := sha256.Sum256([]byte(verifier))
	return base64.RawURLEncoding.EncodeToString(sum[:])
}

var noRedirectClient = &http.Client{
	CheckRedirect: func(*http.Request, []*http.Request) error { return http.ErrUseLastResponse },
}

func getNoRedirect(t *testing.T, url string) *http.Response {
	t.Helper()
	resp, err := noRedirectClient.Get(url)
	if err != nil {
		t.Fatalf("get %s: %v", url, err)
	}
	return resp
}

// startFakeForgejo stands up the Forgejo API surface we need: SDK
// version probe, OIDC userinfo, OAuth token endpoint, plus an /api/v1/user
// for forgejo-mcp's own startup probe.
func startFakeForgejo(t *testing.T) *httptest.Server {
	t.Helper()
	mux := http.NewServeMux()
	mux.HandleFunc("/api/v1/version", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = io.WriteString(w, `{"version":"11.0.0"}`)
	})
	mux.HandleFunc("/api/v1/user", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = io.WriteString(w, `{"id":1,"login":"e2e-user","username":"e2e-user","full_name":"E2E"}`)
	})
	mux.HandleFunc("/login/oauth/access_token", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = io.WriteString(w,
			`{"access_token":"fj-access-token","refresh_token":"fj-refresh-token","token_type":"bearer","expires_in":3600}`)
	})
	mux.HandleFunc("/login/oauth/userinfo", func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = io.WriteString(w, `{"sub":"42","preferred_username":"e2e-user","name":"E2E User"}`)
	})
	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		t.Logf("fake forgejo: unexpected probe %s %s", r.Method, r.URL.Path)
		w.WriteHeader(http.StatusNotFound)
	})
	srv := httptest.NewServer(mux)
	t.Cleanup(srv.Close)
	return srv
}

// buildForgejoMCPSibling locates / builds the forgejo-mcp binary the
// broker will spawn. Same search order as internal/bridge's integration
// test.
func buildForgejoMCPSibling(t *testing.T) string {
	t.Helper()
	if p := os.Getenv("FORGEJO_MCP_BIN"); p != "" {
		if _, err := os.Stat(p); err == nil {
			return p
		}
		t.Skipf("FORGEJO_MCP_BIN=%q does not exist", p)
	}
	if abs, err := filepath.Abs("../../../forgejo-mcp/forgejo-mcp"); err == nil {
		if _, err := os.Stat(abs); err == nil {
			return abs
		}
	}
	if abs, err := filepath.Abs("../../../forgejo-mcp"); err == nil {
		if _, err := os.Stat(filepath.Join(abs, "main.go")); err == nil {
			bin := filepath.Join(t.TempDir(), "forgejo-mcp")
			build := exec.Command("go", "build", "-o", bin, ".")
			build.Dir = abs
			build.Env = os.Environ()
			out, err := build.CombinedOutput()
			if err != nil {
				t.Skipf("go build of sibling forgejo-mcp failed: %v\n%s", err, out)
			}
			return bin
		}
	}
	t.Skip("forgejo-mcp binary not found: set $FORGEJO_MCP_BIN or place a sibling repo at ../forgejo-mcp")
	return ""
}