refactor: extract generic graphql client

pkg/graphql.go

@@ -0,0 +1,79 @@
+package graphql
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+)
+
+type Error struct {
+	Message string `json:"message"`
+}
+
+type Response[T any] struct {
+	Data   T       `json:"data"`
+	Errors []Error `json:"errors"`
+}
+
+type PostOptions struct {
+	Headers map[string]string
+	BodyMax int64
+}
+
+func Post[T any](ctx context.Context, httpClient *http.Client, url string, query string, variables any, opts PostOptions) (T, error) {
+	var zero T
+
+	payload := map[string]any{
+		"query":     query,
+		"variables": variables,
+	}
+
+	body, err := json.Marshal(payload)
+	if err != nil {
+		return zero, fmt.Errorf("graphql: marshal payload: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
+	if err != nil {
+		return zero, fmt.Errorf("graphql: create request: %w", err)
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	for k, v := range opts.Headers {
+		req.Header.Set(k, v)
+	}
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		return zero, fmt.Errorf("graphql: execute request: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	max := opts.BodyMax
+	if max <= 0 {
+		max = 2 << 20
+	}
+
+	respBody, err := io.ReadAll(io.LimitReader(resp.Body, max))
+	if err != nil {
+		return zero, fmt.Errorf("graphql: read response: %w", err)
+	}
+
+	if resp.StatusCode != http.StatusOK {
+		return zero, fmt.Errorf("graphql: status %d", resp.StatusCode)
+	}
+
+	var parsed Response[T]
+	if err := json.Unmarshal(respBody, &parsed); err != nil {
+		return zero, fmt.Errorf("graphql: decode response: %w", err)
+	}
+
+	if len(parsed.Errors) > 0 {
+		return zero, fmt.Errorf("graphql: %s", parsed.Errors[0].Message)
+	}
+
+	return parsed.Data, nil
+}