package jsonrpc2

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"isle/toolkit"
	"net/http"
)

// HTTPClient makes JSONRPC2 requests over an HTTP endpoint.
//
// Close should be called once the HTTPClient is not longer needed.
type HTTPClient struct {
	c   toolkit.HTTPClient
	url string
}

// NewHTTPClient returns an HTTPClient which will use HTTP POST requests against
// the given URL as a transport for JSONRPC2 method calls.
func NewHTTPClient(httpClient toolkit.HTTPClient, urlStr string) *HTTPClient {
	return &HTTPClient{
		c:   httpClient,
		url: urlStr,
	}
}

func (c *HTTPClient) Call(
	ctx context.Context, rcv any, method string, args ...any,
) error {
	var (
		body = new(bytes.Buffer)
		enc  = json.NewEncoder(body)
	)

	id, err := encodeRequest(ctx, enc, method, args)
	if err != nil {
		return fmt.Errorf("encoding request: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, "POST", c.url, body)
	if err != nil {
		return fmt.Errorf("constructing POST request to %q: %w", c.url, err)
	}

	res, err := c.c.Do(req)
	if err != nil {
		return fmt.Errorf("performing request: %w", err)
	}
	defer res.Body.Close()

	dec := json.NewDecoder(res.Body)

	resID, err := decodeResponse(dec, rcv)
	if errors.As(err, new(Error)) {
		return err
	} else if err != nil {
		return fmt.Errorf("decoding response: %w", err)
	} else if resID != id {
		return fmt.Errorf(
			"expected response with ID %q, got %q", id, resID,
		)
	}

	return nil
}

func (c *HTTPClient) Close() error {
	return c.c.Close()
}