package erpconnector

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

	"cmroubao/backend-api/internal/domain"
)

var (
	ErrNotConfigured   = errors.New("ERP connector is not configured")
	ErrSessionRequired = errors.New("ERP session is required")
	ErrNotFound        = errors.New("ERP freight order not found")
	ErrUnavailable     = errors.New("ERP connector is unavailable")
	ErrProtocol        = errors.New("ERP connector protocol is invalid")
)

const maxResponseBytes = 4 << 20

type Client struct {
	baseURL string
	apiKey  string
	http    *http.Client
}

func New(baseURL, apiKey string, timeout time.Duration) (*Client, error) {
	if strings.TrimSpace(baseURL) == "" {
		baseURL = "http://127.0.0.1:8091"
	}
	if timeout <= 0 {
		timeout = 90 * time.Second
	}
	if timeout <= 0 {
		return nil, errors.New("ERP connector client configuration is invalid")
	}
	return &Client{
		baseURL: strings.TrimRight(baseURL, "/"),
		apiKey:  strings.TrimSpace(apiKey),
		http: &http.Client{
			Timeout: timeout,
			CheckRedirect: func(
				_ *http.Request,
				_ []*http.Request,
			) error {
				return http.ErrUseLastResponse
			},
		},
	}, nil
}

func (client *Client) QueryOrder(
	ctx context.Context,
	orderNumber string,
) (domain.FreightSourceBatch, error) {
	if client.apiKey == "" {
		return domain.FreightSourceBatch{}, ErrNotConfigured
	}
	body, err := json.Marshal(map[string]string{"order_number": orderNumber})
	if err != nil {
		return domain.FreightSourceBatch{}, ErrProtocol
	}
	request, err := http.NewRequestWithContext(
		ctx,
		http.MethodPost,
		client.baseURL+"/v1/freight/query",
		bytes.NewReader(body),
	)
	if err != nil {
		return domain.FreightSourceBatch{}, ErrUnavailable
	}
	request.Header.Set("Content-Type", "application/json")
	request.Header.Set("X-API-Key", client.apiKey)
	response, err := client.http.Do(request)
	if err != nil {
		return domain.FreightSourceBatch{}, ErrUnavailable
	}
	defer response.Body.Close()
	limited := io.LimitReader(response.Body, maxResponseBytes+1)
	content, err := io.ReadAll(limited)
	if err != nil || len(content) > maxResponseBytes {
		return domain.FreightSourceBatch{}, ErrUnavailable
	}
	if response.StatusCode != http.StatusOK {
		switch response.StatusCode {
		case http.StatusUnauthorized:
			return domain.FreightSourceBatch{}, ErrSessionRequired
		case http.StatusNotFound:
			return domain.FreightSourceBatch{}, ErrNotFound
		default:
			return domain.FreightSourceBatch{}, ErrUnavailable
		}
	}
	var result domain.FreightSourceBatch
	decoder := json.NewDecoder(bytes.NewReader(content))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&result); err != nil {
		return domain.FreightSourceBatch{}, ErrProtocol
	}
	var extra any
	if err := decoder.Decode(&extra); !errors.Is(err, io.EOF) {
		return domain.FreightSourceBatch{}, ErrProtocol
	}
	if result.SchemaVersion != 1 || result.Query.Mode != "ORDER_NUMBER" ||
		result.Orders == nil {
		return domain.FreightSourceBatch{}, ErrProtocol
	}
	return result, nil
}