/*
 * TencentBlueKing is pleased to support the open source community by making
 * 蓝鲸智云 - 配置平台 (BlueKing - CMDB) available.
 * Copyright (C) 2025 Tencent. All rights reserved.
 * Licensed under the MIT License (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at http://opensource.org/licenses/MIT
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 * We undertake not to change the open source license (MIT license) applicable
 * to the current version of the project delivered to anyone in the future.
 */

package rest

import (
	"bytes"
	"context"
	"encoding/json/v2"
	"errors"
	"fmt"
	"io"
	"maps"
	"net"
	"net/http"
	"net/url"
	"path"
	"reflect"
	"strings"
	"time"

	"go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp"

	"git.ifooth.com/common/pkg/rest/transport"
	"git.ifooth.com/common/pkg/version"
)

var (
	// ErrUnsupported is an error to check supported type or content-type
	ErrUnsupported = errors.New("unsupported")
	userAgent      = fmt.Sprintf("pkg/%s", version.Version)
)

// defaultTransport default transport, same as http.DefaultTransport but change MaxIdleConns / MaxIdleConnsPerHost
var defaultTransport = &http.Transport{
	Proxy: http.ProxyFromEnvironment,
	DialContext: (&net.Dialer{
		Timeout:   30 * time.Second,
		KeepAlive: 30 * time.Second,
	}).DialContext,
	ForceAttemptHTTP2:     true,
	MaxIdleConns:          200, // 最大空闲连接数
	MaxIdleConnsPerHost:   20,  // 每个主机的最大空闲连接数
	IdleConnTimeout:       30 * time.Second,
	TLSHandshakeTimeout:   10 * time.Second,
	ExpectContinueTimeout: 1 * time.Second,
}

// HTTPClient a http.Client or rest.Client Do interface
type HTTPClient interface {
	Do(*http.Request) (*http.Response, error)
}

// Client is a HTTP client with common url, header, params and transports.
type Client struct {
	baseTransport     http.RoundTripper
	transports        []func(http.RoundTripper) http.RoundTripper
	baseURL           *url.URL
	timeout           time.Duration
	commonHeader      http.Header
	commonQueryParams url.Values
	err               error
}

// NewClient creates a new client
func NewClient() *Client {
	commonHeader := make(http.Header)
	commonHeader.Set("User-Agent", userAgent)

	// 默认统一添加trace
	baseTransport := otelhttp.NewTransport(defaultTransport)

	c := &Client{
		baseTransport:     baseTransport,
		commonQueryParams: make(url.Values),
		commonHeader:      commonHeader,
	}

	return c
}

func (c *Client) parseBaseURL(baseURL string) (*url.URL, error) {
	if baseURL == "" {
		return nil, fmt.Errorf("baseURL is required")
	}

	u, err := url.Parse(baseURL)
	if err != nil {
		return nil, fmt.Errorf("baseURL %s not valid, err: %w", baseURL, err)
	}

	if u.Host == "" || u.Scheme == "" {
		return nil, fmt.Errorf("baseURL %s not valid, host/schema is required", baseURL)
	}

	return u, nil
}

// SetBaseURL sets the base URL for the client.
func (c *Client) SetBaseURL(baseURL string) *Client {
	c.baseURL, c.err = c.parseBaseURL(baseURL)
	return c
}

// SetTimeout set a timeout for the client.
func (c *Client) SetTimeout(timeout time.Duration) *Client {
	c.timeout = timeout
	return c
}

// SetHeader set the common header for the client.
func (c *Client) SetHeader(header, value string) *Client {
	c.commonHeader.Set(header, value)
	return c
}

// SetQueryParam set the common query param for the client.
func (c *Client) SetQueryParam(param, value string) *Client {
	c.commonQueryParams.Set(param, value)
	return c
}

// SetTransport set the base transport for the client.
func (c *Client) SetTransport(transport http.RoundTripper) *Client {
	if transport != nil {
		c.baseTransport = transport
	}

	return c
}

// GetTransport return the http.RoundTripper by chaining the transports for client.
func (c *Client) GetTransport() http.RoundTripper {
	// freeze transports
	next := c.chain()

	rt := func(req *http.Request) (*http.Response, error) {
		newReq, err := c.finalReq(req)
		if err != nil {
			return nil, err
		}

		return next.RoundTrip(newReq)
	}

	return transport.RoundTripFunc(rt)
}

// With adds inline http.RoundTripper for an base RoundTripper for the client.
func (c *Client) With(rt ...func(http.RoundTripper) http.RoundTripper) *Client {
	c.transports = append(c.transports, rt...)
	return c
}

func (c *Client) chain() http.RoundTripper {
	rt := c.baseTransport

	for i := len(c.transports) - 1; i >= 0; i-- {
		rt = c.transports[i](rt)
	}

	return rt
}

// mergeURL return the merged url with common header and params
func (c *Client) mergeURL(u *url.URL) (*url.URL, error) {
	query := make(url.Values)

	if c.baseURL != nil {
		if u.Host != "" || u.Scheme != "" {
			return nil, fmt.Errorf("baseURL and request url host/schema can not be set at the same time")
		}

		u.Scheme = c.baseURL.Scheme
		u.Host = c.baseURL.Host
		u.Path = path.Join(c.baseURL.Path, u.Path)
		maps.Copy(query, c.baseURL.Query())
	}

	// change the url query
	maps.Copy(query, c.commonQueryParams)
	maps.Copy(query, u.Query())
	u.RawQuery = query.Encode()

	return u, nil
}

func (c *Client) finalReq(req *http.Request) (*http.Request, error) {
	if c.err != nil {
		return nil, c.err
	}

	newReq := req.Clone(req.Context())

	u, err := c.mergeURL(newReq.URL)
	if err != nil {
		return nil, err
	}
	newReq.URL = u

	// change the req header
	header := make(http.Header)
	maps.Copy(header, c.commonHeader)
	maps.Copy(header, newReq.Header)
	newReq.Header = header

	return newReq, nil
}

// Do implement HTTPClient interface, same as the http.Client
func (c *Client) Do(req *http.Request) (*http.Response, error) {
	newReq, err := c.finalReq(req)
	if err != nil {
		return nil, err
	}

	httpClient := &http.Client{Transport: c.chain(), Timeout: c.timeout}
	return httpClient.Do(newReq)
}

// Request is a generic HTTP request with response type T
type Request[T any] struct {
	client      HTTPClient
	req         *http.Request
	transports  []func(http.RoundTripper) http.RoundTripper
	queryParams url.Values
	body        any
	timeout     time.Duration
}

// R create a new request with the default client and response type T
func R[T any]() *Request[T] {
	req := &http.Request{Header: make(http.Header)}
	req = req.WithContext(context.Background())

	r := &Request[T]{
		client:      NewClient(), // default client and transport
		req:         req,
		queryParams: make(url.Values),
	}

	return r
}

// SetClient set the rest.Client or http.Client for the request.
func (r *Request[T]) SetClient(client HTTPClient) *Request[T] {
	r.client = client
	return r
}

// With adds inline http.RoundTripper for the request.
func (r *Request[T]) With(rt ...func(http.RoundTripper) http.RoundTripper) *Request[T] {
	r.transports = append(r.transports, rt...)
	return r
}

// SetTimeout set a timeout for the current request.
func (r *Request[T]) SetTimeout(timeout time.Duration) *Request[T] {
	r.timeout = timeout
	return r
}

// SetHeader set the request header for the request.
func (r *Request[T]) SetHeader(header, value string) *Request[T] {
	r.req.Header.Set(header, value)
	return r
}

// SetQueryParam set the request header for the request.
func (r *Request[T]) SetQueryParam(param, value string) *Request[T] {
	r.queryParams.Set(param, value)
	return r
}

// SetContext set the request header for the request.
func (r *Request[T]) SetContext(ctx context.Context) *Request[T] {
	r.req = r.req.WithContext(ctx)
	return r
}

// SetBody set the request body for the request.
func (r *Request[T]) SetBody(body any) *Request[T] {
	r.body = body
	return r
}

// Get execute a get request
func (r *Request[T]) Get(url string, args ...any) (*T, error) {
	return r.Execute(http.MethodGet, url, args...)
}

// Post execute a post request
func (r *Request[T]) Post(url string, args ...any) (*T, error) {
	return r.Execute(http.MethodPost, url, args...)
}

// Put execute a put request
func (r *Request[T]) Put(url string, args ...any) (*T, error) {
	return r.Execute(http.MethodPut, url, args...)
}

// Patch execute a patch request
func (r *Request[T]) Patch(url string, args ...any) (*T, error) {
	return r.Execute(http.MethodPatch, url, args...)
}

// Delete execute a delete request
func (r *Request[T]) Delete(url string, args ...any) (*T, error) {
	return r.Execute(http.MethodDelete, url, args...)
}

// getBody get body reader or marshal reader
func (r *Request[T]) getBody() (io.Reader, error) {
	if r.body == nil {
		return nil, nil
	}

	switch body := r.body.(type) {
	case []byte:
		return bytes.NewReader(body), nil
	case string:
		return strings.NewReader(body), nil
	case io.Reader:
		return body, nil
	default:
		// continue check kind below
	}

	rv := reflect.ValueOf(r.body)
	if rv.Kind() == reflect.Pointer {
		rv = rv.Elem()
	}

	switch rv.Kind() {
	case reflect.Map, reflect.Slice, reflect.Struct:
		body, err := json.Marshal(r.body)
		if err != nil {
			return nil, err
		}
		r.SetHeader("Content-Type", "application/json")

		return bytes.NewReader(body), nil
	default:
		// continue check kind below
	}

	return nil, fmt.Errorf("%w body type: %T", ErrUnsupported, r.body)
}

// getURL get the final url for the request.
func (r *Request[T]) getURL(u string) (string, error) {
	newURL, err := url.Parse(u)
	if err != nil {
		return "", err
	}

	// change the url query
	query := newURL.Query()
	maps.Copy(query, r.queryParams)

	newURL.RawQuery = query.Encode()

	return newURL.String(), nil
}

// withStdHTTPClient chain with http Client and request transports
func (r *Request[T]) withStdHTTPClient(c *http.Client) HTTPClient {
	rt := c.Transport
	if rt == nil {
		rt = http.DefaultTransport
	}

	for i := len(r.transports) - 1; i >= 0; i-- {
		rt = r.transports[i](rt)
	}

	newC := *c
	newC.Transport = rt
	return &newC
}

// withRestClient chain with rest client and request transports
func (r *Request[T]) withRestClient(c *Client) HTTPClient {
	newTransports := make([]func(http.RoundTripper) http.RoundTripper, len(c.transports))
	copy(newTransports, c.transports)

	newC := *c
	newC.transports = newTransports

	// append request transports
	newC.With(r.transports...)

	return &newC
}

func (r *Request[T]) getHTTPClient() HTTPClient {
	switch c := r.client.(type) {
	case *Client:
		return r.withRestClient(c)
	case *http.Client:
		return r.withStdHTTPClient(c)
	default:
		// will ignore request transport
		return c
	}
}

// Execute execute a request with method and url
func (r *Request[T]) Execute(method string, url string, args ...any) (*T, error) {
	body, err := r.getBody()
	if err != nil {
		return nil, err
	}

	// fix non-constant format string in call
	if len(args) > 0 {
		url = fmt.Sprintf(url, args...)
	}

	finalURL, err := r.getURL(url)
	if err != nil {
		return nil, err
	}

	newReq, err := http.NewRequestWithContext(r.req.Context(), method, finalURL, body)
	if err != nil {
		return nil, err
	}

	// change the req header
	maps.Copy(newReq.Header, r.req.Header)

	if r.timeout > 0 {
		ctx, cancel := context.WithTimeout(newReq.Context(), r.timeout)
		defer cancel()

		newReq = newReq.WithContext(ctx)
	}

	client := r.getHTTPClient()
	resp, err := client.Do(newReq)
	if err != nil {
		return nil, err
	}

	return r.handleResp(resp)
}

func (r *Request[T]) handleResp(resp *http.Response) (*T, error) {
	out := new(T)

	// io.ReadCloser 需要自己调用Close
	switch any(out).(type) {
	case *http.Response:
		return any(resp).(*T), nil
	case *io.ReadCloser:
		return any(&resp.Body).(*T), nil
	case *Response: // for additional trace info, reuse body and so on
		r := Response{Response: resp, receivedAt: time.Now()}
		return any(&r).(*T), nil
	default:
		// continue check kind below
	}

	// body 自动close
	defer resp.Body.Close()

	// 需要读取整个body
	switch any(out).(type) {
	case *[]byte:
		body, err := io.ReadAll(resp.Body)
		if err != nil {
			return nil, err
		}
		return any(&body).(*T), nil
	case *string:
		body, err := io.ReadAll(resp.Body)
		if err != nil {
			return nil, err
		}
		v := string(body)
		return any(&v).(*T), nil
	case *io.Reader:
		body, err := io.ReadAll(resp.Body)
		if err != nil {
			return nil, err
		}
		v := io.Reader(bytes.NewBuffer(body))
		return any(&v).(*T), nil
	default:
		// continue check kind below
	}

	rt := reflect.TypeFor[T]()

	// 其他只处理json, 自定义序列化请使用[]byte或者io.Reader
	switch rt.Kind() {
	case reflect.Map, reflect.Slice, reflect.Struct:
		if err := json.UnmarshalRead(resp.Body, out); err != nil {
			return nil, err
		}
		return out, nil
	default:
		// continue check kind below
	}

	return nil, fmt.Errorf("%w type: %v", ErrUnsupported, rt)
}

// Response struct holds response values of executed requests.
type Response struct {
	*http.Response
	receivedAt time.Time
}

// ReceivedAt method returns the time we received a response from the server for the request.
func (r *Response) ReceivedAt() time.Time {
	return r.receivedAt
}