initial commits

src/nexus_claude_api/routes/messages.py

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+from __future__ import annotations
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, Request
+from fastapi.responses import JSONResponse, Response, StreamingResponse
+from pydantic import ValidationError
+
+from nexus_claude_api.errors import NexusClaudeError, anthropic_error_response
+from nexus_claude_api.models import (
+    AnthropicMessagesRequest,
+    CountTokensRequest,
+    CountTokensResponse,
+)
+from nexus_claude_api.nexus_client import NexusClient
+from nexus_claude_api.tokens import estimate_input_tokens
+from nexus_claude_api.translators.anthropic_to_bedrock import anthropic_to_bedrock_request
+from nexus_claude_api.translators.bedrock_to_anthropic import bedrock_to_anthropic_response
+from nexus_claude_api.translators.stream import (
+    bedrock_stream_to_anthropic_events,
+    sse_frame,
+)
+
+
+router = APIRouter()
+
+
+def get_nexus_client(request: Request) -> NexusClient:
+    return request.app.state.nexus_client
+
+
+@router.post("/v1/messages", response_model=None)
+async def create_message(
+    request: Request,
+    client: Annotated[NexusClient, Depends(get_nexus_client)],
+) -> Response:
+    try:
+        raw = await request.json()
+        payload = AnthropicMessagesRequest.model_validate(raw)
+        bedrock_request = anthropic_to_bedrock_request(payload)
+        if payload.stream:
+            stream = client.converse_stream(bedrock_request)
+            return StreamingResponse(
+                (
+                    sse_frame(event)
+                    for event in bedrock_stream_to_anthropic_events(
+                        stream,
+                        model=payload.model,
+                    )
+                ),
+                media_type="text/event-stream",
+            )
+
+        response = client.converse(bedrock_request)
+        anthropic_response = bedrock_to_anthropic_response(
+            response,
+            model=payload.model,
+        )
+        return JSONResponse(content=anthropic_response.model_dump(exclude_none=True))
+    except ValidationError as exc:
+        return anthropic_error_response(str(exc), status_code=400)
+    except NexusClaudeError as exc:
+        return anthropic_error_response(
+            exc.message,
+            status_code=exc.status_code,
+            error_type=exc.error_type,
+        )
+
+
+@router.post("/v1/messages/count_tokens")
+async def count_tokens(request: Request) -> JSONResponse:
+    try:
+        raw = await request.json()
+        payload = CountTokensRequest.model_validate(raw)
+        response = CountTokensResponse(input_tokens=estimate_input_tokens(payload))
+        return JSONResponse(content=response.model_dump())
+    except ValidationError as exc:
+        return anthropic_error_response(str(exc), status_code=400)