chore: establish YCode replication baseline and TODO

src/main/gateway/index.ts

@@ -0,0 +1,179 @@
+/**
+ * 自建模型网关（OpenAI 兼容）。
+ *
+ * 职责：
+ *  1. 持有上游 baseUrl / apiKey（永不进入渲染进程）
+ *  2. 按配置地址选择 Chat Completions / Responses + SSE 流式
+ *  3. 把上游的增量 delta 组装成「文本增量」与「完整工具调用」两类输出
+ *
+ * 设计约束：网关只做协议适配与组装，不含业务策略；
+ * 模型路由、上下文裁剪、工具编排由上层（agent/loop.ts）负责。
+ */
+
+import type { GatewayConfig, ToolSpec } from '@shared/types'
+import { resolveOpenAIEndpoint } from '@shared/openai-endpoint'
+import { parseSse } from './sse'
+import { buildResponsesRequest, parseResponsesStream } from './responses'
+
+/** 上游 wire 格式的消息 */
+export interface WireMessage {
+  role: 'system' | 'user' | 'assistant' | 'tool'
+  content: string | null | Array<{ type: 'text'; text: string } | { type: 'image_url'; image_url: { url: string } }>
+  tool_calls?: WireToolCall[]
+  tool_call_id?: string
+}
+
+export interface WireToolCall {
+  id: string
+  type: 'function'
+  function: { name: string; arguments: string }
+}
+
+/** 网关输出的增量事件 */
+export type GatewayDelta =
+  | { type: 'text'; text: string }
+  | { type: 'reasoning'; text: string }
+  | { type: 'tool_calls'; calls: WireToolCall[] }
+  | { type: 'finish'; reason: string | null }
+
+export interface GatewayStreamRequest {
+  messages: WireMessage[]
+  tools?: ToolSpec[]
+  signal?: AbortSignal
+}
+
+export class GatewayError extends Error {
+  constructor(
+    message: string,
+    readonly status?: number,
+    readonly body?: string
+  ) {
+    super(message)
+    this.name = 'GatewayError'
+  }
+}
+
+export class Gateway {
+  constructor(private readonly config: GatewayConfig) {}
+
+  async *stream(req: GatewayStreamRequest): AsyncGenerator<GatewayDelta, void, void> {
+    if (!this.config.apiKey && this.config.authMode !== 'none') {
+      throw new GatewayError('未配置 API Key，请先在设置中填写')
+    }
+    if (!this.config.baseUrl) {
+      throw new GatewayError('未配置上游地址（baseUrl）')
+    }
+
+    let endpoint: ReturnType<typeof resolveOpenAIEndpoint>
+    try { endpoint = resolveOpenAIEndpoint(this.config.baseUrl) } catch { throw new GatewayError('上游地址格式无效') }
+    const responses = endpoint.api === 'openai-responses'
+    const body: Record<string, unknown> = responses ? buildResponsesRequest(this.config, req) : {
+      model: this.config.model,
+      messages: req.messages,
+      stream: true,
+      temperature: this.config.temperature
+    }
+    if (!responses && this.config.maxOutputTokens) body.max_tokens = this.config.maxOutputTokens
+    if (!responses && req.tools && req.tools.length > 0) {
+      body.tools = req.tools
+      body.tool_choice = 'auto'
+    }
+
+    let res: Response
+    try {
+      res = await fetch(endpoint.endpoint, {
+        method: 'POST',
+        headers: {
+          'content-type': 'application/json',
+          accept: 'text/event-stream',
+          ...(this.config.apiKey ? { authorization: `Bearer ${this.config.apiKey}` } : {})
+        },
+        body: JSON.stringify(body),
+        signal: req.signal
+      })
+    } catch (err) {
+      if ((err as Error).name === 'AbortError') throw err
+      throw new GatewayError(responses ? '无法连接 Responses 上游' : `无法连接上游：${(err as Error).message}`)
+    }
+
+    if (!res.ok || !res.body) {
+      // A Responses provider can echo request credentials in arbitrary error bodies.
+      const text = responses ? undefined : await safeReadText(res)
+      if (responses) await res.body?.cancel().catch(() => {})
+      throw new GatewayError(
+        responses ? `Responses 上游返回 HTTP ${res.status}` : `上游返回 ${res.status} ${res.statusText}`.trim(),
+        res.status,
+        text
+      )
+    }
+
+    if (responses) {
+      yield* parseResponsesStream(res.body, (message) => new GatewayError(message), req.signal)
+      return
+    }
+
+    // 累加器：按 index 归并流式工具调用分片
+    const acc = new Map<number, { id: string; name: string; args: string }>()
+    let finishReason: string | null = null
+
+    for await (const evt of parseSse(res.body)) {
+      if (evt.data === '[DONE]') break
+
+      let payload: any
+      try {
+        payload = JSON.parse(evt.data)
+      } catch {
+        continue // 非 JSON 的心跳/注释行直接跳过
+      }
+
+      if (payload?.error) {
+        throw new GatewayError(
+          `上游错误：${payload.error.message ?? JSON.stringify(payload.error)}`
+        )
+      }
+
+      const choice = payload?.choices?.[0]
+      if (!choice) continue
+      const delta = choice.delta ?? {}
+
+      if (typeof delta.content === 'string' && delta.content.length > 0) {
+        yield { type: 'text', text: delta.content }
+      }
+      if (typeof delta.reasoning_content === 'string' && delta.reasoning_content.length > 0) {
+        yield { type: 'reasoning', text: delta.reasoning_content }
+      }
+
+      if (Array.isArray(delta.tool_calls)) {
+        for (const piece of delta.tool_calls) {
+          const idx = typeof piece.index === 'number' ? piece.index : 0
+          const slot = acc.get(idx) ?? { id: '', name: '', args: '' }
+          if (piece.id) slot.id = piece.id
+          if (piece.function?.name) slot.name = piece.function.name
+          if (piece.function?.arguments) slot.args += piece.function.arguments
+          acc.set(idx, slot)
+        }
+      }
+
+      if (choice.finish_reason) finishReason = choice.finish_reason
+    }
+
+    const calls: WireToolCall[] = [...acc.entries()]
+      .sort((a, b) => a[0] - b[0])
+      .map(([idx, slot]) => ({
+        id: slot.id || `call_${idx}_${Date.now()}`,
+        type: 'function' as const,
+        function: { name: slot.name, arguments: slot.args || '{}' }
+      }))
+
+    if (calls.length > 0) yield { type: 'tool_calls', calls }
+    yield { type: 'finish', reason: finishReason }
+  }
+}
+
+async function safeReadText(res: Response): Promise<string> {
+  try {
+    return (await res.text()).slice(0, 2000)
+  } catch {
+    return ''
+  }
+}