package jsonrpc2

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

	"dev.mediocregopher.com/mediocre-go-lib.git/mlog"
)

type DivideParams struct {
	Top, Bottom int
}

var ErrDivideByZero = Error{
	Code:    1,
	Message: "Cannot divide by zero",
}

type dividerImpl struct{}

func (dividerImpl) Divide(ctx context.Context, p DivideParams) (int, error) {
	if p.Bottom == 0 {
		return 0, ErrDivideByZero
	}
	if p.Top%p.Bottom != 0 {
		return 0, errors.New("numbers don't divide evenly, cannot compute!")
	}
	return p.Top / p.Bottom, nil
}

func (dividerImpl) Hidden(ctx context.Context, p struct{}) (int, error) {
	return 0, errors.New("Shouldn't be possible to call this!")
}

type divider interface {
	Divide(ctx context.Context, p DivideParams) (int, error)
}

var testHandler = func() Handler {
	var (
		logger = mlog.NewLogger(&mlog.LoggerOpts{
			MaxLevel: mlog.LevelDebug.Int(),
		})

		d = divider(dividerImpl{})
	)

	return Chain(
		NewMLogMiddleware(logger),
		ExposeServerSideErrorsMiddleware,
	)(
		NewDispatchHandler(&d),
	)
}()

func testClient(t *testing.T, client Client) {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	t.Run("success/no_result", func(t *testing.T) {
		err := client.Call(ctx, nil, "Divide", DivideParams{12, 4})
		if err != nil {
			t.Fatal(err)
		}
	})

	t.Run("success/with_result", func(t *testing.T) {
		var res int
		err := client.Call(ctx, &res, "Divide", DivideParams{6, 3})
		if err != nil {
			t.Fatal(err)
		} else if res != 2 {
			t.Fatalf("expected 2, got %d", res)
		}
	})

	t.Run("err/application", func(t *testing.T) {
		err := client.Call(ctx, nil, "Divide", DivideParams{})
		if !errors.Is(err, ErrDivideByZero) {
			t.Fatalf("expected application error but got: %#v", err)
		}
	})

	t.Run("err/calling hidden method", func(t *testing.T) {
		err := client.Call(ctx, nil, "Hidden", struct{}{})
		if jErr := (Error{}); !errors.As(err, &jErr) {
			t.Fatalf("expected RPC error but got: %#v", err)
		} else if jErr.Code != errCodeMethodNotFound {
			t.Fatalf("expected method not found error but got: %#v", jErr)
		}
	})

	t.Run("err/sever-side error", func(t *testing.T) {
		err := client.Call(ctx, nil, "Divide", DivideParams{6, 4})
		t.Log(err)
		if jErr := (Error{}); !errors.As(err, &jErr) {
			t.Fatalf("expected RPC error but got: %#v", err)
		} else if jErr.Code != errCodeServerError {
			t.Fatalf("expected server error but got: %#v", jErr)
		} else if !strings.Contains(jErr.Message, "cannot compute!") {
			t.Fatalf("expected server-side error message to be propagated but got: %#v", jErr)
		}
	})
}

func TestReadWriter(t *testing.T) {
	type (
		rw struct {
			io.Reader
			io.Writer
		}
	)

	var (
		ctx = context.Background()

		clientReader, handlerWriter = io.Pipe()
		handlerReader, clientWriter = io.Pipe()

		clientRW  = rw{clientReader, clientWriter}
		handlerRW = rw{handlerReader, handlerWriter}

		server = NewReadWriterServer(testHandler, handlerRW)
		client = NewReadWriterClient(clientRW)

		wg = new(sync.WaitGroup)
	)

	defer wg.Wait()
	defer clientWriter.Close()
	defer handlerWriter.Close()

	wg.Add(1)
	go func() {
		defer wg.Done()
		for {
			if err := server.HandleNext(ctx); errors.Is(err, io.EOF) {
				return
			} else if err != nil {
				return
			}
		}
	}()

	testClient(t, client)
}

func TestHTTP(t *testing.T) {
	server := httptest.NewServer(NewHTTPHandler(testHandler))
	t.Cleanup(server.Close)
	testClient(t, NewHTTPClient(server.URL))
}