package ai

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

// client is a small LLM HTTP client with a bounded response size and a
// timeout so a slow or chatty upstream cannot hang a scan.
type client struct {
	httpc *http.Client
}

func newClient() *client {
	return &client{httpc: &http.Client{Timeout: 60 * time.Second}}
}

// postJSON sends payload as JSON and decodes the response body into out.
func (c *client) postJSON(ctx context.Context, url string, headers map[string]string, payload, out any) error {
	body, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("ai: encode request: %w", err)
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("ai: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	for k, v := range headers {
		req.Header.Set(k, v)
	}

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

	data, err := io.ReadAll(io.LimitReader(resp.Body, 4<<20)) // 4 MiB cap
	if err != nil {
		return fmt.Errorf("ai: read response: %w", err)
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("ai: %s: %s", resp.Status, strings.TrimSpace(string(data)))
	}
	if err := json.Unmarshal(data, out); err != nil {
		return fmt.Errorf("ai: decode response: %w", err)
	}
	return nil
}