// Package chaos 提供基于 toxiproxy 的弱网故障注入辅助。
// 上游地址由调用方传入，不写死端口。
package chaos

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

// Client 调用 toxiproxy HTTP API。
type Client struct {
	BaseURL    string
	HTTPClient *http.Client
}

// NewClient 创建客户端。baseURL 形如 http://127.0.0.1:8474。
func NewClient(baseURL string) *Client {
	return &Client{
		BaseURL: strings.TrimRight(baseURL, "/"),
		HTTPClient: &http.Client{
			Timeout: 10 * time.Second,
		},
	}
}

// Proxy 描述一个 toxiproxy 代理。
type Proxy struct {
	Name     string `json:"name"`
	Listen   string `json:"listen"`
	Upstream string `json:"upstream"`
	Enabled  bool   `json:"enabled"`
}

// Toxic 描述一条故障规则。
type Toxic struct {
	Name       string         `json:"name"`
	Type       string         `json:"type"`
	Stream     string         `json:"stream,omitempty"`
	Toxicity   float32        `json:"toxicity,omitempty"`
	Attributes map[string]any `json:"attributes,omitempty"`
}

// CreateProxy 创建或覆盖同名代理。listen 可用 host:0 让 toxiproxy 分配端口。
func (c *Client) CreateProxy(name, listen, upstream string) (*Proxy, error) {
	if name == "" {
		return nil, fmt.Errorf("proxy name required")
	}
	if listen == "" {
		return nil, fmt.Errorf("listen required")
	}
	if upstream == "" {
		return nil, fmt.Errorf("upstream required")
	}
	body := Proxy{
		Name:     name,
		Listen:   listen,
		Upstream: upstream,
		Enabled:  true,
	}
	var out Proxy
	if err := c.doJSON(http.MethodPost, "/proxies", body, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// DeleteProxy 删除代理；不存在时忽略。
func (c *Client) DeleteProxy(name string) error {
	req, err := http.NewRequest(http.MethodDelete, c.BaseURL+"/proxies/"+name, nil)
	if err != nil {
		return err
	}
	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode == http.StatusNotFound || resp.StatusCode == http.StatusNoContent || resp.StatusCode == http.StatusOK {
		return nil
	}
	b, _ := io.ReadAll(resp.Body)
	return fmt.Errorf("delete proxy: %s: %s", resp.Status, strings.TrimSpace(string(b)))
}

// GetProxy 读取代理（含实际 listen 地址）。
func (c *Client) GetProxy(name string) (*Proxy, error) {
	var out Proxy
	if err := c.doJSON(http.MethodGet, "/proxies/"+name, nil, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// AddLatency 注入下行/上行延迟（毫秒）。stream 为空时默认 downstream。
func (c *Client) AddLatency(proxyName, toxicName string, latencyMs, jitterMs int, stream string) (*Toxic, error) {
	if stream == "" {
		stream = "downstream"
	}
	t := Toxic{
		Name:     toxicName,
		Type:     "latency",
		Stream:   stream,
		Toxicity: 1,
		Attributes: map[string]any{
			"latency": latencyMs,
			"jitter":  jitterMs,
		},
	}
	return c.addToxic(proxyName, t)
}

// AddResetPeer 在连接上注入 TCP RST（断开）。timeoutMs 为触发前等待。
func (c *Client) AddResetPeer(proxyName, toxicName string, timeoutMs int, stream string) (*Toxic, error) {
	if stream == "" {
		stream = "downstream"
	}
	t := Toxic{
		Name:     toxicName,
		Type:     "reset_peer",
		Stream:   stream,
		Toxicity: 1,
		Attributes: map[string]any{
			"timeout": timeoutMs,
		},
	}
	return c.addToxic(proxyName, t)
}

// RemoveToxic 删除一条 toxic。
func (c *Client) RemoveToxic(proxyName, toxicName string) error {
	req, err := http.NewRequest(http.MethodDelete, c.BaseURL+"/proxies/"+proxyName+"/toxics/"+toxicName, nil)
	if err != nil {
		return err
	}
	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	if resp.StatusCode == http.StatusNotFound || resp.StatusCode == http.StatusNoContent || resp.StatusCode == http.StatusOK {
		return nil
	}
	b, _ := io.ReadAll(resp.Body)
	return fmt.Errorf("remove toxic: %s: %s", resp.Status, strings.TrimSpace(string(b)))
}

func (c *Client) addToxic(proxyName string, t Toxic) (*Toxic, error) {
	var out Toxic
	if err := c.doJSON(http.MethodPost, "/proxies/"+proxyName+"/toxics", t, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

func (c *Client) doJSON(method, path string, in any, out any) error {
	var body io.Reader
	if in != nil {
		b, err := json.Marshal(in)
		if err != nil {
			return err
		}
		body = bytes.NewReader(b)
	}
	req, err := http.NewRequest(method, c.BaseURL+path, body)
	if err != nil {
		return err
	}
	if in != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return err
	}
	defer func() { _ = resp.Body.Close() }()
	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return err
	}
	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return fmt.Errorf("%s %s: %s: %s", method, path, resp.Status, strings.TrimSpace(string(respBody)))
	}
	if out == nil || len(respBody) == 0 {
		return nil
	}
	return json.Unmarshal(respBody, out)
}