feat: ModelRouter — unified OpenAI-compatible multi-source LLM gateway

- Lua adapters per upstream (transform_request/response/stream_chunk, build_headers signing hooks)
- AUTO priority routing with per-model kind (chat/image), explicit source/model routing
- Per-source concurrency caps with queueing, exponential backoff, AUTO failover
- OpenAI-compatible API: chat completions, SSE streaming, image generations, models
- Gateway key auth, web UI for adapter/source management, runtime persistence
- e2e test running the real binary against mocked upstreams

internal/lua/adapters/kimicode.lua

@@ -0,0 +1,107 @@
+local adapter = {}
+
+adapter.name = "kimicode"
+adapter.version = "1.0.0"
+adapter.endpoint = "/v1/chat/completions"
+adapter.headers = {}
+
+-- KimiCode / Kimi K2 属于 OpenAI 兼容协议；但部分云端 API 会校验调用方
+-- "app"（只放行特定 agent），要求每次请求带上按 secret 计算的应用签名。
+-- 这里演示 build_headers 钩子：基于 timestamp + 请求体哈希生成签名头。
+--
+-- 配置要求（source.meta）:
+--   meta:
+--     app_id:   <申请到的 app id>
+--     app_key:  <你的 key（由网关的 base_url 复用 api_key 亦可）>
+--     app_secret: <签名密钥>
+--     app_agent: code-agent   # 若云端要求声明 agent 身份
+function adapter.transform_request(raw_body)
+    local ok, req = pcall(json.decode, raw_body)
+    if not ok then return raw_body end
+    req.model = req.model or "kimi-k2"
+    req.disable_thinking = nil
+    req.extra_body = nil
+    return json.encode(req)
+end
+
+-- 可选的动态签名钩子。meta 由 Go 注入：
+--   meta.url / meta.method / meta.body / meta.api_key / meta.timestamp / meta.source.meta
+function adapter.build_headers(meta)
+    local h = {
+        ["Content-Type"] = "application/json",
+        ["X-App-Id"] = tostring((meta.source.meta or {}).app_id or ""),
+        ["X-Timestamp"] = tostring(meta.timestamp),
+    }
+    local agent = (meta.source.meta or {}).app_agent
+    if agent and agent ~= "" then
+        h["X-Agent"] = agent
+    end
+    -- 校验 app：通常要求 Authorization 用 app secret 派生签名
+    local secret = (meta.source.meta or {}).app_secret
+    local api_key = meta.source.meta and meta.source.meta.api_key or meta.api_key
+    if secret and secret ~= "" then
+        local body_hash = sha256_hex(meta.body)
+        local sign_string = tostring(meta.timestamp) .. meta.method .. meta.url .. body_hash
+        local sign = hmac_sha256_hex(secret, sign_string)
+        h["Authorization"] = "Bearer " .. api_key
+        h["X-App-Sign"] = sign
+    else
+        h["Authorization"] = "Bearer " .. api_key
+    end
+    return h
+end
+
+function adapter.transform_response(raw_body)
+    local ok, resp = pcall(json.decode, raw_body)
+    if not ok or resp == nil then return raw_body end
+
+    local unified = {
+        content = "",
+        finish_reason = "",
+        token_usage = { prompt = 0, completion = 0, total = 0 }
+    }
+    if type(resp.usage) == "table" then
+        unified.token_usage.prompt = resp.usage.prompt_tokens or 0
+        unified.token_usage.completion = resp.usage.completion_tokens or 0
+        unified.token_usage.total = resp.usage.total_tokens or 0
+    end
+    if type(resp.choices) == "table" and #resp.choices > 0 then
+        local ch = resp.choices[1]
+        if type(ch.message) == "table" then
+            unified.content = ch.message.content or ""
+            if ch.message.reasoning_content then
+                unified.reasoning_content = ch.message.reasoning_content
+            end
+            if type(ch.message.tool_calls) == "table" then
+                local tcs = {}
+                for _, tc in ipairs(ch.message.tool_calls) do
+                    local args_ok, args = pcall(json.decode, tc["function"].arguments)
+                    if not args_ok then args = {} end
+                    table.insert(tcs, {
+                        id = tc.id,
+                        type = tc.type or "function",
+                        name = tc["function"].name,
+                        arguments = args
+                    })
+                end
+                unified.tool_calls = tcs
+            end
+        end
+        unified.finish_reason = ch.finish_reason or ""
+    end
+    return json.encode(unified)
+end
+
+function adapter.transform_stream_chunk(raw_chunk)
+    local ok, chunk = pcall(json.decode, raw_chunk)
+    if not ok then return "" end
+    if not chunk.choices or #chunk.choices == 0 then return "" end
+    local delta = chunk.choices[1].delta or {}
+    local fr = chunk.choices[1].finish_reason
+    return json.encode({
+        content = delta.content or "",
+        done = (fr ~= nil)
+    })
+end
+
+return adapter