package agentserver

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

// ErrNotFound 上游返回 404
var ErrNotFound = errors.New("agentserver: not found")

// Client AgentServer HTTP 客户端，使用平台 API Key 鉴权。
// 管理类请求（会话创建/改名/删除、归属反查）使用带超时的 http.Client；
// 代理转发（含 SSE 长连接）使用不设整体超时的 streamHTTP，由调用方的 context 控制生命周期。
type Client struct {
	baseURL    string
	apiKey     string
	http       *http.Client
	streamHTTP *http.Client
}

// NewClient 创建客户端；baseURL 形如 http://127.0.0.1:8787（不含 /v1）
func NewClient(baseURL, apiKey string) *Client {
	transport := &http.Transport{
		Proxy:               nil, // 内网服务，不走系统代理
		MaxIdleConns:        100,
		MaxIdleConnsPerHost: 50,
		IdleConnTimeout:     90 * time.Second,
	}
	return &Client{
		baseURL:    strings.TrimRight(baseURL, "/"),
		apiKey:     apiKey,
		http:       &http.Client{Transport: transport, Timeout: 30 * time.Second},
		streamHTTP: &http.Client{Transport: transport},
	}
}

// Configured 是否已配置地址和 API Key
func (c *Client) Configured() bool {
	return c != nil && c.baseURL != "" && c.apiKey != ""
}

// Forward 转发一次请求（代理用）：path 以 /v1/ 开头，rawQuery 不含问号。
// 返回的响应由调用方负责关闭 Body。
func (c *Client) Forward(ctx context.Context, method, path, rawQuery string, header http.Header, body io.Reader) (*http.Response, error) {
	u := c.baseURL + path
	if rawQuery != "" {
		u += "?" + rawQuery
	}
	req, err := http.NewRequestWithContext(ctx, method, u, body)
	if err != nil {
		return nil, err
	}
	for k, vs := range header {
		for _, v := range vs {
			req.Header.Add(k, v)
		}
	}
	req.Header.Set("Authorization", "Bearer "+c.apiKey)
	return c.streamHTTP.Do(req)
}

// CreateSession POST /v1/sessions；profileId 为空时使用 API Key 的默认 Profile
func (c *Client) CreateSession(ctx context.Context, profileId string) (*SessionDto, error) {
	body := map[string]any{}
	if profileId != "" {
		body["profileId"] = profileId
	}
	var out SessionDto
	if err := c.doJSON(ctx, http.MethodPost, "/v1/sessions", body, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// PatchSession PATCH /v1/sessions/:id
func (c *Client) PatchSession(ctx context.Context, sessionId string, body map[string]any) error {
	return c.doJSON(ctx, http.MethodPatch, "/v1/sessions/"+url.PathEscape(sessionId), body, nil)
}

// DeleteSession DELETE /v1/sessions/:id；上游已不存在时视为成功
func (c *Client) DeleteSession(ctx context.Context, sessionId string) error {
	err := c.doJSON(ctx, http.MethodDelete, "/v1/sessions/"+url.PathEscape(sessionId), nil, nil)
	if errors.Is(err, ErrNotFound) {
		return nil
	}
	return err
}

// GetRun GET /v1/runs/:id（归属反查用）
func (c *Client) GetRun(ctx context.Context, runId string) (*RunDto, error) {
	var out RunDto
	if err := c.doJSON(ctx, http.MethodGet, "/v1/runs/"+url.PathEscape(runId), nil, &out); err != nil {
		return nil, err
	}
	return &out, nil
}

// ListFiles GET /v1/sessions/:id/files（归属反查用）
func (c *Client) ListFiles(ctx context.Context, sessionId string) ([]FileDto, error) {
	var out []FileDto
	if err := c.doJSON(ctx, http.MethodGet, "/v1/sessions/"+url.PathEscape(sessionId)+"/files", nil, &out); err != nil {
		return nil, err
	}
	return out, nil
}

// PendingInteractions GET /v1/interactions?sessionId=（归属反查用）
func (c *Client) PendingInteractions(ctx context.Context, sessionId string) ([]InteractionRefDto, error) {
	var out []InteractionRefDto
	if err := c.doJSON(ctx, http.MethodGet, "/v1/interactions?sessionId="+url.QueryEscape(sessionId), nil, &out); err != nil {
		return nil, err
	}
	return out, nil
}

func (c *Client) doJSON(ctx context.Context, 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.NewRequestWithContext(ctx, method, c.baseURL+path, body)
	if err != nil {
		return err
	}
	req.Header.Set("Authorization", "Bearer "+c.apiKey)
	if in != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("请求 AgentServer 失败: %w", err)
	}
	defer resp.Body.Close()
	data, _ := io.ReadAll(io.LimitReader(resp.Body, 16<<20))
	if resp.StatusCode == http.StatusNotFound {
		return ErrNotFound
	}
	if resp.StatusCode >= 300 {
		var eb ErrorBody
		if json.Unmarshal(data, &eb) == nil && eb.Error.Message != "" {
			return fmt.Errorf("AgentServer %d %s: %s", resp.StatusCode, eb.Error.Code, eb.Error.Message)
		}
		return fmt.Errorf("AgentServer %d: %s", resp.StatusCode, truncate(string(data), 200))
	}
	if out != nil && len(data) > 0 {
		if err := json.Unmarshal(data, out); err != nil {
			return fmt.Errorf("解析 AgentServer 响应失败: %w", err)
		}
	}
	return nil
}

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