// Package backend is the typed HTTP client for Dialectic.Backend's API.
// Endpoint shapes mirror Dialectic.OpenclawPlugin/plugin/src/backend-client.ts
// so the two plugins drop into the same backend without per-plugin
// adapters.
package backend

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

type Client struct {
	BaseURL string
	APIKey  string
	HTTP    *http.Client
}

func New(baseURL, apiKey string) *Client {
	return &Client{
		BaseURL: strings.TrimRight(baseURL, "/"),
		APIKey:  apiKey,
		HTTP:    &http.Client{Timeout: 15 * time.Second},
	}
}

func (c *Client) Get(ctx context.Context, path string) (json.RawMessage, error) {
	return c.do(ctx, http.MethodGet, path, nil)
}

func (c *Client) Post(ctx context.Context, path string, body any) (json.RawMessage, error) {
	return c.do(ctx, http.MethodPost, path, body)
}

func (c *Client) Put(ctx context.Context, path string, body any) (json.RawMessage, error) {
	return c.do(ctx, http.MethodPut, path, body)
}

func (c *Client) do(ctx context.Context, method, path string, body any) (json.RawMessage, error) {
	if c.APIKey == "" {
		return nil, errors.New("dialectic api key not configured — set plugins.dialectic.config.apiKey or agentKeys[<agent_id>]")
	}
	url := c.BaseURL + ensureLeadingSlash(path)
	var rdr io.Reader
	if body != nil {
		raw, err := json.Marshal(body)
		if err != nil {
			return nil, fmt.Errorf("marshal %s %s: %w", method, path, err)
		}
		rdr = bytes.NewReader(raw)
	}
	req, err := http.NewRequestWithContext(ctx, method, url, rdr)
	if err != nil {
		return nil, err
	}
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	req.Header.Set("Authorization", "Bearer "+c.APIKey)
	req.Header.Set("Accept", "application/json")

	res, err := c.HTTP.Do(req)
	if err != nil {
		return nil, fmt.Errorf("%s %s: %w", method, path, err)
	}
	defer res.Body.Close()
	raw, _ := io.ReadAll(res.Body)
	if res.StatusCode < 200 || res.StatusCode >= 300 {
		return nil, fmt.Errorf("%s %s → %d: %s",
			method, path, res.StatusCode, truncate(raw, 500))
	}
	if len(raw) == 0 {
		return nil, nil
	}
	return raw, nil
}

func ensureLeadingSlash(p string) string {
	if strings.HasPrefix(p, "/") {
		return p
	}
	return "/" + p
}

func truncate(b []byte, n int) string {
	if len(b) <= n {
		return string(b)
	}
	return string(b[:n]) + "…"
}

// TopicDetail is the minimal shape the signup tool needs (debate window
// for HF pre-check). The Dialectic backend returns more fields — they
// pass through untouched in the raw JSON the tools surface to agents.
type TopicDetail struct {
	ID            string `json:"id"`
	DebateStartAt string `json:"debate_start_at"`
	DebateEndAt   string `json:"debate_end_at"`
}