package jsonrpc2

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"sync"
	"testing"
	"time"

	"github.com/sirupsen/logrus"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// ---------- helpers ----------

func newTestRPCServer(t *testing.T) *RPCServer {
	t.Helper()

	logger := logrus.New()
	logger.SetOutput(io.Discard) // silence logs during tests

	srv, err := NewRPCServer("test-rpc", logger)
	require.NoError(t, err)

	srv.SetMaxBodySize(1024)

	return srv
}

func postJSON(h http.Handler, body string) *httptest.ResponseRecorder {
	req := httptest.NewRequest(
		http.MethodPost,
		"/rpc",
		bytes.NewBufferString(body),
	)

	req.Header.Set("Content-Type", "application/json")

	rec := httptest.NewRecorder()
	h.ServeHTTP(rec, req)

	return rec
}

func parseResponse(
	t *testing.T,
	rec *httptest.ResponseRecorder,
) map[string]any {
	t.Helper()

	var resp map[string]any

	err := json.Unmarshal(rec.Body.Bytes(), &resp)
	require.NoError(t, err)

	return resp
}

// ---------- basic ----------

func TestPing(t *testing.T) {
	srv := newTestRPCServer(t)

	rec := postJSON(
		srv,
		`{"jsonrpc":"2.0","method":"ping","id":1}`,
	)

	assert.Equal(t, http.StatusOK, rec.Code)

	resp := parseResponse(t, rec)

	assert.Equal(t, "2.0", resp["jsonrpc"])
	assert.Equal(t, "pong", resp["result"])
	assert.Equal(t, float64(1), resp["id"])
}

func TestNotification(t *testing.T) {
	srv := newTestRPCServer(t)

	rec := postJSON(
		srv,
		`{"jsonrpc":"2.0","method":"ping"}`,
	)

	assert.Equal(t, http.StatusOK, rec.Code)
	assert.Empty(t, rec.Body.String())
}

func TestOnlyPOST(t *testing.T) {
	srv := newTestRPCServer(t)

	req := httptest.NewRequest(http.MethodGet, "/rpc", nil)
	rec := httptest.NewRecorder()

	srv.ServeHTTP(rec, req)

	assert.Equal(t, http.StatusMethodNotAllowed, rec.Code)
}

func TestMethodNotFound(t *testing.T) {
	srv := newTestRPCServer(t)

	rec := postJSON(
		srv,
		`{"jsonrpc":"2.0","method":"unknown","id":1}`,
	)

	assert.Equal(t, http.StatusOK, rec.Code)

	resp := parseResponse(t, rec)

	errObj, ok := resp["error"].(map[string]any)
	require.True(t, ok)

	assert.Equal(t, float64(-32601), errObj["code"])
	assert.Contains(t, errObj["message"], "Method not found")
}

func TestInvalidJSON(t *testing.T) {
	srv := newTestRPCServer(t)

	rec := postJSON(srv, `{invalid json}`)

	assert.Equal(t, http.StatusOK, rec.Code)

	resp := parseResponse(t, rec)

	errObj, ok := resp["error"].(map[string]any)
	require.True(t, ok)

	assert.Equal(t, float64(-32700), errObj["code"])
}

func TestBatchRejected(t *testing.T) {
	srv := newTestRPCServer(t)

	rec := postJSON(
		srv,
		`[{"jsonrpc":"2.0","method":"ping","id":1}]`,
	)

	assert.Equal(t, http.StatusOK, rec.Code)

	resp := parseResponse(t, rec)

	errObj, ok := resp["error"].(map[string]any)
	require.True(t, ok)

	assert.Equal(t, float64(-32600), errObj["code"])
}

func TestRequestBodyTooLarge(t *testing.T) {
	srv := newTestRPCServer(t)

	srv.SetMaxBodySize(10)

	rec := postJSON(
		srv,
		`{"jsonrpc":"2.0","method":"ping","id":1}`,
	)

	assert.Equal(t, http.StatusBadRequest, rec.Code)
}

// ---------- handler ----------

func TestHandlerPanic(t *testing.T) {
	srv := newTestRPCServer(t)

	err := srv.RegisterMethods(MethodMap{
		"panic.method": func(
			ctx context.Context,
			req *Request,
		) *Response {
			panic("boom")
		},
	})

	require.NoError(t, err)

	rec := postJSON(
		srv,
		`{"jsonrpc":"2.0","method":"panic.method","id":1}`,
	)

	assert.Equal(t, http.StatusOK, rec.Code)

	resp := parseResponse(t, rec)

	errObj, ok := resp["error"].(map[string]any)
	require.True(t, ok)

	assert.Equal(t, float64(-32603), errObj["code"])
}

func TestNilHandlerResponse(t *testing.T) {
	srv := newTestRPCServer(t)

	err := srv.RegisterMethods(MethodMap{
		"nil.response": func(
			ctx context.Context,
			req *Request,
		) *Response {
			return nil
		},
	})

	require.NoError(t, err)

	rec := postJSON(
		srv,
		`{"jsonrpc":"2.0","method":"nil.response","id":1}`,
	)

	assert.Equal(t, http.StatusOK, rec.Code)

	resp := parseResponse(t, rec)

	assert.Nil(t, resp["result"])
}

// ---------- register ----------

func TestRegisterMethodsAtomic(t *testing.T) {
	srv := newTestRPCServer(t)

	err := srv.RegisterMethods(MethodMap{
		"a": func(
			ctx context.Context,
			req *Request,
		) *Response {
			return BuildResponse(req, "ok", nil)
		},
	})

	require.NoError(t, err)

	err = srv.RegisterMethods(MethodMap{
		"b": nil, // invalid
	})

	assert.Error(t, err)
	assert.NotContains(t, srv.ListMethods(), "b")
}

func TestListMethodsSorted(t *testing.T) {
	srv := newTestRPCServer(t)

	err := srv.RegisterMethods(MethodMap{
		"z": func(
			ctx context.Context,
			req *Request,
		) *Response {
			return nil
		},
		"a": func(
			ctx context.Context,
			req *Request,
		) *Response {
			return nil
		},
	})

	require.NoError(t, err)

	methods := srv.ListMethods()

	assert.Equal(
		t,
		[]string{"a", "ping", "z"},
		methods,
	)
}

// ---------- concurrency ----------

func TestConcurrentRequests(t *testing.T) {
	srv := newTestRPCServer(t)

	err := srv.RegisterMethods(MethodMap{
		"echo": func(
			ctx context.Context,
			req *Request,
		) *Response {
			time.Sleep(10 * time.Millisecond)
			return BuildResponse(req, "ok", nil)
		},
	})

	require.NoError(t, err)

	const workers = 100

	var wg sync.WaitGroup
	errCh := make(chan error, workers)

	for i := 0; i < workers; i++ {
		wg.Add(1)

		go func(id int) {
			defer wg.Done()

			body := fmt.Sprintf(
				`{"jsonrpc":"2.0","method":"echo","id":%d}`,
				id,
			)

			rec := postJSON(srv, body)

			if rec.Code != http.StatusOK {
				errCh <- fmt.Errorf(
					"id=%d status=%d",
					id,
					rec.Code,
				)
			}
		}(i)
	}

	wg.Wait()
	close(errCh)

	for err := range errCh {
		t.Error(err)
	}
}

// ---------- lifecycle ----------

func TestStopCancelsHandlers(t *testing.T) {
	srv := newTestRPCServer(t)

	done := make(chan struct{})

	err := srv.RegisterMethods(MethodMap{
		"block": func(
			ctx context.Context,
			req *Request,
		) *Response {
			<-ctx.Done()
			close(done)

			return BuildResponse(
				req,
				"canceled",
				nil,
			)
		},
	})

	require.NoError(t, err)

	go func() {
		postJSON(
			srv,
			`{"jsonrpc":"2.0","method":"block","id":1}`,
		)
	}()

	time.Sleep(50 * time.Millisecond)

	srv.Stop()

	select {
	case <-done:
	case <-time.After(time.Second):
		t.Fatal("handler was not canceled after Stop()")
	}
}