package proxy_test

import (
	"context"
	"errors"
	"io"
	"net/http"
	"net/http/httptest"
	"net/netip"
	"net/url"
	"strings"
	"sync/atomic"
	"testing"
	"time"

	"git.misaka.ren/M1saka/token_thief/config"
	"git.misaka.ren/M1saka/token_thief/proxy"
)

type failingBody struct{ err error }

func (b failingBody) Read([]byte) (int, error) { return 0, b.err }
func (failingBody) Close() error               { return nil }

type lateFailingBody struct {
	remaining int
	err       error
}

func (b *lateFailingBody) Read(p []byte) (int, error) {
	if b.remaining == 0 {
		return 0, b.err
	}
	n := min(len(p), b.remaining)
	for i := range p[:n] {
		p[i] = 'x'
	}
	b.remaining -= n
	return n, nil
}

func (*lateFailingBody) Close() error { return nil }

type failingResponseWriter struct {
	header http.Header
	short  bool
}

func (w *failingResponseWriter) Header() http.Header { return w.header }
func (*failingResponseWriter) WriteHeader(int)       {}
func (w *failingResponseWriter) Write(p []byte) (int, error) {
	if w.short {
		return len(p) - 1, nil
	}
	return 0, errors.New("write failed")
}

func newTestHandler(t *testing.T, upstream *url.URL, sub *captureSubmitter, opts proxy.Options) *proxy.Handler {
	t.Helper()
	filter, err := config.NewFilter(config.FilterDisabled, nil)
	if err != nil {
		t.Fatal(err)
	}
	return proxy.NewWithOptions(upstream, filter, sub, 1024*1024, opts)
}

func TestRequestBodyReadFailureReturnsFixed400WithoutUpstream(t *testing.T) {
	var upstreamCalls atomic.Int32
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		upstreamCalls.Add(1)
		w.WriteHeader(http.StatusOK)
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	h := newTestHandler(t, u, &captureSubmitter{}, proxy.Options{})

	req := httptest.NewRequest(http.MethodPost, "http://proxy.test/v1/chat", nil)
	req.Body = failingBody{err: errors.New("secret read failure")}
	req.ContentLength = 1
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	if rec.Code != http.StatusBadRequest || rec.Body.String() != "bad request\n" {
		t.Fatalf("response=(%d, %q), want fixed 400 bad request", rec.Code, rec.Body.String())
	}
	if upstreamCalls.Load() != 0 {
		t.Fatalf("upstream called %d times", upstreamCalls.Load())
	}
}

func TestRequestBodyReadFailureAfterCaptureLimitDoesNotReachUpstream(t *testing.T) {
	var upstreamCalls atomic.Int32
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		upstreamCalls.Add(1)
		_, _ = io.Copy(io.Discard, r.Body)
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	h := newTestHandler(t, u, &captureSubmitter{}, proxy.Options{})

	req := httptest.NewRequest(http.MethodPost, "http://proxy.test/v1/chat", nil)
	req.Body = &lateFailingBody{remaining: 1024*1024 + 1, err: errors.New("late read failure")}
	req.ContentLength = 1024*1024 + 2
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	if rec.Code != http.StatusBadRequest || rec.Body.String() != "bad request\n" {
		t.Fatalf("response=(%d, %q), want fixed 400 bad request", rec.Code, rec.Body.String())
	}
	if upstreamCalls.Load() != 0 {
		t.Fatalf("upstream called %d times", upstreamCalls.Load())
	}
}

func TestFilteredRequestBodyReadFailureDoesNotReachUpstream(t *testing.T) {
	var upstreamCalls atomic.Int32
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		upstreamCalls.Add(1)
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	filter, err := config.NewFilter(config.FilterBlacklist, []string{"/ignored"})
	if err != nil {
		t.Fatal(err)
	}
	h := proxy.NewWithOptions(u, filter, &captureSubmitter{}, 1024, proxy.Options{})

	req := httptest.NewRequest(http.MethodPost, "http://proxy.test/ignored", nil)
	req.Body = failingBody{err: errors.New("read failure")}
	req.ContentLength = 1
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	if rec.Code != http.StatusBadRequest || rec.Body.String() != "bad request\n" {
		t.Fatalf("response=(%d, %q), want fixed 400 bad request", rec.Code, rec.Body.String())
	}
	if upstreamCalls.Load() != 0 {
		t.Fatalf("upstream called %d times", upstreamCalls.Load())
	}
}

func TestBadGatewayResponseDoesNotLeakUpstreamError(t *testing.T) {
	badURL, _ := url.Parse("http://127.0.0.1:1")
	h := newTestHandler(t, badURL, &captureSubmitter{}, proxy.Options{})
	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, httptest.NewRequest(http.MethodGet, "http://proxy.test/v1/test", nil))

	if rec.Code != http.StatusBadGateway || rec.Body.String() != "bad gateway\n" {
		t.Fatalf("response=(%d, %q), want fixed 502 bad gateway", rec.Code, rec.Body.String())
	}
}

func TestResponseWriteFailurePreventsCommit(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = io.WriteString(w, "response")
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)

	for _, short := range []bool{false, true} {
		sub := &captureSubmitter{}
		h := newTestHandler(t, u, sub, proxy.Options{})
		w := &failingResponseWriter{header: make(http.Header), short: short}
		h.ServeHTTP(w, httptest.NewRequest(http.MethodGet, "http://proxy.test/v1/test", nil))
		if sub.Len() != 0 {
			t.Fatalf("short=%v: failed response write was committed", short)
		}
	}
}

func TestTrustedProxyClientIP(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		_, _ = io.WriteString(w, "ok")
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	trusted := netip.MustParsePrefix("10.0.0.0/8")

	tests := []struct {
		name   string
		peer   string
		xff    string
		wantIP string
	}{
		{name: "untrusted peer ignores xff", peer: "203.0.113.9:1234", xff: "198.51.100.1", wantIP: "203.0.113.9"},
		{name: "strip trusted from right", peer: "10.0.0.2:1234", xff: "198.51.100.7, 10.0.0.3", wantIP: "198.51.100.7"},
		{name: "ipv6", peer: "[2001:db8::2]:1234", xff: "198.51.100.7", wantIP: "2001:db8::2"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			sub := &captureSubmitter{}
			h := newTestHandler(t, u, sub, proxy.Options{TrustedProxies: []netip.Prefix{trusted}})
			req := httptest.NewRequest(http.MethodGet, "http://proxy.test/v1/test", nil)
			req.RemoteAddr = tc.peer
			req.Header.Set("X-Forwarded-For", tc.xff)
			h.ServeHTTP(httptest.NewRecorder(), req)
			if sub.Len() != 1 || sub.Entry(0).ClientIP != tc.wantIP {
				t.Fatalf("ClientIP=%q, want %q", sub.Entry(0).ClientIP, tc.wantIP)
			}
		})
	}
}

func TestTrustedProxyUsesValidXRealIPWithoutXFF(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	sub := &captureSubmitter{}
	trusted := netip.MustParsePrefix("192.0.2.0/24")
	h := newTestHandler(t, u, sub, proxy.Options{TrustedProxies: []netip.Prefix{trusted}})
	req := httptest.NewRequest(http.MethodGet, "http://proxy.test/x", nil)
	req.RemoteAddr = "192.0.2.10:1234"
	req.Header.Set("X-Real-IP", "198.51.100.20")
	h.ServeHTTP(httptest.NewRecorder(), req)
	if sub.Len() != 1 || sub.Entry(0).ClientIP != "198.51.100.20" {
		t.Fatalf("entries=%d", sub.Len())
	}
}

func TestResponseBodyTimeoutPreventsCommit(t *testing.T) {
	release := make(chan struct{})
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusOK)
		w.(http.Flusher).Flush()
		<-release
	}))
	u, _ := url.Parse(upstream.URL)
	sub := &captureSubmitter{}
	h := newTestHandler(t, u, sub, proxy.Options{ResponseTimeout: 50 * time.Millisecond})

	srv := httptest.NewServer(h)
	resp, err := http.Get(srv.URL + "/v1/test")
	if err == nil {
		_, _ = io.ReadAll(resp.Body)
		_ = resp.Body.Close()
	}
	time.Sleep(50 * time.Millisecond)
	if sub.Len() != 0 {
		t.Fatal("timed out response must not be committed")
	}
	close(release)
	srv.Close()
	upstream.Close()
}

func TestSSEIdleTimeoutResetsAfterReads(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/event-stream")
		f := w.(http.Flusher)
		for _, event := range []string{"data: one\n\n", "data: two\n\n", "data: [DONE]\n\n"} {
			_, _ = io.WriteString(w, event)
			f.Flush()
			time.Sleep(30 * time.Millisecond)
		}
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	sub := &captureSubmitter{}
	h := newTestHandler(t, u, sub, proxy.Options{SSEIdleTimeout: 60 * time.Millisecond})
	srv := httptest.NewServer(h)
	defer srv.Close()

	resp, err := http.Get(srv.URL + "/v1/test")
	if err != nil {
		t.Fatal(err)
	}
	_, _ = io.ReadAll(resp.Body)
	_ = resp.Body.Close()
	if sub.Len() != 1 {
		t.Fatalf("entries=%d, want completed SSE commit", sub.Len())
	}
}

func TestIncompleteSSEEventPreventsCommit(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/event-stream")
		_, _ = io.WriteString(w, "data: partial")
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	sub := &captureSubmitter{}
	h := newTestHandler(t, u, sub, proxy.Options{})

	h.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(http.MethodGet, "http://proxy.test/v1/test", nil))
	if sub.Len() != 0 {
		t.Fatal("SSE ending mid-event must not be committed as complete")
	}
}

func TestIncompleteSSEEventAfterTerminalEventPreventsCommit(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "text/event-stream")
		_, _ = io.WriteString(w, "data: [DONE]\n\n")
		w.(http.Flusher).Flush()
		_, _ = io.WriteString(w, "data: partial")
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	sub := &captureSubmitter{}
	h := newTestHandler(t, u, sub, proxy.Options{})

	h.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(http.MethodGet, "http://proxy.test/v1/test", nil))
	if sub.Len() != 0 {
		t.Fatal("SSE ending mid-event after a terminal event must not be committed")
	}
}

func TestShutdownReturnsWithoutHijackedConnections(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.WriteHeader(http.StatusOK) }))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	h := newTestHandler(t, u, &captureSubmitter{}, proxy.Options{})
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	if err := h.Shutdown(ctx); err != nil {
		t.Fatal(err)
	}
}

func TestTerminalTextInNonSSEBodyDoesNotAffectCommit(t *testing.T) {
	upstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Content-Type", "application/json")
		_, _ = io.WriteString(w, `{"text":"data: [DONE]"}`)
	}))
	defer upstream.Close()
	u, _ := url.Parse(upstream.URL)
	sub := &captureSubmitter{}
	h := newTestHandler(t, u, sub, proxy.Options{})
	h.ServeHTTP(httptest.NewRecorder(), httptest.NewRequest(http.MethodGet, "http://proxy.test/v1/test", strings.NewReader("")))
	if sub.Len() != 1 {
		t.Fatalf("entries=%d, want 1", sub.Len())
	}
}