package auth

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

type ExchangeResponse struct {
	ErrorCode string         `json:"errorCode"`
	ErrorMsg  string         `json:"errorMsg"`
	Message   string         `json:"message"`
	Body      map[string]any `json:"body"`
}

func ExchangeCode(client *http.Client, endpoint string, code string, decryptKey string) (Credentials, error) {
	if strings.TrimSpace(endpoint) == "" {
		return Credentials{}, errors.New("exchange endpoint is required")
	}
	if strings.TrimSpace(code) == "" {
		return Credentials{}, errors.New("code is required")
	}
	if strings.TrimSpace(decryptKey) == "" {
		return Credentials{}, errors.New("decrypt key is required")
	}
	if client == nil {
		client = &http.Client{Timeout: 60 * time.Second}
	}

	body, _ := json.Marshal(map[string]string{"code": code})
	req, err := http.NewRequest(http.MethodPost, endpoint, bytes.NewReader(body))
	if err != nil {
		return Credentials{}, err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := client.Do(req)
	if err != nil {
		return Credentials{}, err
	}
	defer resp.Body.Close()

	var exchange ExchangeResponse
	if err := json.NewDecoder(resp.Body).Decode(&exchange); err != nil {
		return Credentials{}, err
	}
	if exchange.ErrorCode != "Success" {
		msg := firstNonEmpty(exchange.ErrorMsg, exchange.Message, exchange.ErrorCode)
		return Credentials{}, fmt.Errorf("exchange failed: %s", msg)
	}

	ak, err := decryptBodyField(exchange.Body, "ak", decryptKey)
	if err != nil {
		return Credentials{}, err
	}
	sk, err := decryptBodyField(exchange.Body, "sk", decryptKey)
	if err != nil {
		return Credentials{}, err
	}
	token, err := decryptBodyField(exchange.Body, "token", decryptKey)
	if err != nil {
		return Credentials{}, err
	}
	return Credentials{AccessKey: ak, SecretKey: sk, Token: token, SavedAt: time.Now()}, nil
}

func decryptBodyField(body map[string]any, key string, decryptKey string) (string, error) {
	v, ok := body[key]
	if !ok {
		return "", fmt.Errorf("response body missing %s", key)
	}
	s, ok := v.(string)
	if !ok || strings.TrimSpace(s) == "" {
		return "", fmt.Errorf("response body %s is not a string", key)
	}
	return DecryptCredential(strings.TrimSpace(s), decryptKey)
}

func firstNonEmpty(values ...string) string {
	for _, v := range values {
		if strings.TrimSpace(v) != "" {
			return v
		}
	}
	return "unknown error"
}