mcp: add server stdio entry and --help

src/metin_release_mcp/server.py

@@ -1,16 +1,172 @@
-"""MCP server entry point (scaffold).
+"""MCP stdio server entry point.
 
-The real stdio server, tool registration, and dispatch logic land in
-subsequent commits. This stub only advertises the package version so
-``python -m metin_release_mcp`` doesn't crash during the scaffold
-commit.
+Registers each :data:`~metin_release_mcp.tool_defs.TOOL_SPECS` entry as
+an MCP tool. On invocation the handler:
+
+1. Validates input via the tool's JSON schema (enforced by the SDK) and
+   by :func:`~metin_release_mcp.tool_defs.build_cli_args`.
+2. Shells out to ``metin-release <subcommand> --json …`` via
+   :func:`~metin_release_mcp.cli_runner.run_cli`.
+3. Returns the parsed JSON envelope as the MCP tool result.
+
+The server contains **no release business logic**. If the CLI returns a
+non-zero exit or an ``ok=false`` envelope, the wrapper passes that
+envelope back to the caller verbatim, tagging it with the CLI stderr as
+diagnostic text.
 """
 
 from __future__ import annotations
 
+import argparse
+import asyncio
+import json
+import sys
+from typing import Any
+
 from . import __version__
+from .errors import (
+    CliNotFoundError,
+    CliUnparseableOutputError,
+    InvalidToolInputError,
+    McpWrapperError,
+    UnknownToolError,
+)
+from .cli_runner import run_cli
+from .tool_defs import TOOL_SPECS, TOOLS_BY_NAME, build_cli_args, json_schema
+
+
+def _build_mcp_server():  # pragma: no cover - imported lazily for tests
+    from mcp.server import Server
+    from mcp.types import TextContent, Tool
+
+    server = Server("metin-release-mcp", version=__version__)
+
+    @server.list_tools()
+    async def _list_tools() -> list[Tool]:
+        return [
+            Tool(
+                name=spec.name,
+                description=spec.description,
+                inputSchema=json_schema(spec),
+            )
+            for spec in TOOL_SPECS
+        ]
+
+    @server.call_tool()
+    async def _call_tool(name: str, arguments: dict[str, Any] | None):
+        envelope, stderr = dispatch(name, arguments or {})
+        text = json.dumps(envelope, indent=2, sort_keys=False)
+        content = [TextContent(type="text", text=text)]
+        if stderr.strip():
+            content.append(
+                TextContent(type="text", text=f"metin-release stderr:\n{stderr}")
+            )
+        return content, envelope
+
+    return server
+
+
+def dispatch(tool_name: str, payload: dict[str, Any]) -> tuple[dict[str, Any], str]:
+    """Dispatch a tool call synchronously.
+
+    Returns ``(envelope, stderr)``. On wrapper errors the envelope is
+    shaped like the CLI's own ``{"ok": false, "error": {...}}`` error
+    envelope so callers can treat both error sources the same way.
+    """
+    spec = TOOLS_BY_NAME.get(tool_name)
+    if spec is None:
+        raise UnknownToolError(
+            f"unknown tool: {tool_name!r} (known: {sorted(TOOLS_BY_NAME)})"
+        )
+    try:
+        argv_tail = build_cli_args(spec, payload)
+    except InvalidToolInputError as exc:
+        return exc.to_envelope(), ""
+
+    try:
+        result = run_cli(argv_tail)
+    except (CliNotFoundError, CliUnparseableOutputError) as exc:
+        return exc.to_envelope(stderr=None), ""
+
+    return result.envelope, result.stderr
+
+
+def _print_help() -> None:
+    lines = [
+        f"metin-release-mcp {__version__}",
+        "",
+        "Thin MCP server wrapping the metin-release CLI over stdio.",
+        "",
+        "Usage: metin-release-mcp [--help | --version | --list-tools]",
+        "",
+        "With no arguments, runs an MCP server on stdio and registers these tools:",
+        "",
+    ]
+    for spec in TOOL_SPECS:
+        lines.append(f"  {spec.name:<26}  {spec.description}")
+    lines.append("")
+    lines.append("Environment:")
+    lines.append(
+        "  METIN_RELEASE_BINARY   Path to metin-release CLI (else resolved via PATH)"
+    )
+    print("\n".join(lines))
+
+
+def _print_tools() -> None:
+    out = [
+        {"name": s.name, "description": s.description, "inputSchema": json_schema(s)}
+        for s in TOOL_SPECS
+    ]
+    json.dump(out, sys.stdout, indent=2)
+    sys.stdout.write("\n")
+
+
+async def _run_stdio() -> None:  # pragma: no cover - exercised only end-to-end
+    from mcp.server.stdio import stdio_server
+
+    server = _build_mcp_server()
+    async with stdio_server() as (read_stream, write_stream):
+        await server.run(
+            read_stream,
+            write_stream,
+            server.create_initialization_options(),
+        )
 
 
 def main(argv: list[str] | None = None) -> int:
-    print(f"metin-release-mcp {__version__} (scaffold)")
+    parser = argparse.ArgumentParser(
+        prog="metin-release-mcp",
+        description="Thin MCP server wrapping the metin-release CLI.",
+        add_help=False,
+    )
+    parser.add_argument("-h", "--help", action="store_true")
+    parser.add_argument("--version", action="store_true")
+    parser.add_argument(
+        "--list-tools",
+        action="store_true",
+        help="Print registered tool schemas as JSON and exit.",
+    )
+    args = parser.parse_args(argv)
+
+    if args.help:
+        _print_help()
+        return 0
+    if args.version:
+        print(f"metin-release-mcp {__version__}")
+        return 0
+    if args.list_tools:
+        _print_tools()
+        return 0
+
+    try:
+        asyncio.run(_run_stdio())
+    except McpWrapperError as exc:
+        print(json.dumps(exc.to_envelope()), file=sys.stderr)
+        return 1
+    except KeyboardInterrupt:  # pragma: no cover
+        return 130
     return 0
+
+
+if __name__ == "__main__":  # pragma: no cover
+    raise SystemExit(main())