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| 1 | +"""Simple ecommerce MCP server exposing the shopping cart widget.""" |
| 2 | + |
| 3 | +from __future__ import annotations |
| 4 | + |
| 5 | +from pathlib import Path |
| 6 | +from typing import Any, Dict, List |
| 7 | +from uuid import uuid4 |
| 8 | + |
| 9 | +import mcp.types as types |
| 10 | +from mcp.server.fastmcp import FastMCP |
| 11 | +from pydantic import BaseModel, ConfigDict, Field, ValidationError |
| 12 | + |
| 13 | +TOOL_NAME = "add_to_cart" |
| 14 | +WIDGET_TEMPLATE_URI = "ui://widget/shopping-cart.html" |
| 15 | +WIDGET_TITLE = "Start shopping cart" |
| 16 | +WIDGET_INVOKING = "Preparing shopping cart" |
| 17 | +WIDGET_INVOKED = "Shopping cart ready" |
| 18 | +MIME_TYPE = "text/html+skybridge" |
| 19 | +ASSETS_DIR = Path(__file__).resolve().parent.parent / "assets" |
| 20 | + |
| 21 | + |
| 22 | +def _load_widget_html() -> str: |
| 23 | + html_path = ASSETS_DIR / "shopping-cart.html" |
| 24 | + if html_path.exists(): |
| 25 | + return html_path.read_text(encoding="utf8") |
| 26 | + |
| 27 | + fallback = sorted(ASSETS_DIR.glob("shopping-cart-*.html")) |
| 28 | + if fallback: |
| 29 | + return fallback[-1].read_text(encoding="utf8") |
| 30 | + |
| 31 | + raise FileNotFoundError( |
| 32 | + f'Widget HTML for "shopping-cart" not found in {ASSETS_DIR}. ' |
| 33 | + "Run `pnpm run build` to generate the assets before starting the server." |
| 34 | + ) |
| 35 | + |
| 36 | + |
| 37 | +SHOPPING_CART_HTML = _load_widget_html() |
| 38 | + |
| 39 | + |
| 40 | +class CartItem(BaseModel): |
| 41 | + """Represents an item being added to a cart.""" |
| 42 | + |
| 43 | + name: str = Field(..., description="Name of the item to show in the cart.") |
| 44 | + quantity: int = Field( |
| 45 | + default=1, |
| 46 | + ge=1, |
| 47 | + description="How many units to add to the cart (must be positive).", |
| 48 | + ) |
| 49 | + |
| 50 | + model_config = ConfigDict(populate_by_name=True, extra="allow") |
| 51 | + |
| 52 | + |
| 53 | +class AddToCartInput(BaseModel): |
| 54 | + """Payload for the add_to_cart tool.""" |
| 55 | + |
| 56 | + items: List[CartItem] = Field( |
| 57 | + ..., |
| 58 | + description="List of items to add to the active cart.", |
| 59 | + ) |
| 60 | + cart_id: str | None = Field( |
| 61 | + default=None, |
| 62 | + alias="cartId", |
| 63 | + description="Existing cart identifier. Leave blank to start a new cart.", |
| 64 | + ) |
| 65 | + |
| 66 | + model_config = ConfigDict(populate_by_name=True, extra="forbid") |
| 67 | + |
| 68 | + |
| 69 | +TOOL_INPUT_SCHEMA = AddToCartInput.model_json_schema(by_alias=True) |
| 70 | + |
| 71 | +carts: Dict[str, List[Dict[str, Any]]] = {} |
| 72 | + |
| 73 | +mcp = FastMCP( |
| 74 | + name="ecommerce-python", |
| 75 | + stateless_http=True, |
| 76 | +) |
| 77 | + |
| 78 | + |
| 79 | +def _serialize_item(item: CartItem) -> Dict[str, Any]: |
| 80 | + """Return a JSON serializable dict including any custom fields.""" |
| 81 | + return item.model_dump(by_alias=True) |
| 82 | + |
| 83 | + |
| 84 | +def _get_or_create_cart(cart_id: str | None) -> str: |
| 85 | + if cart_id and cart_id in carts: |
| 86 | + return cart_id |
| 87 | + |
| 88 | + new_id = cart_id or uuid4().hex |
| 89 | + carts.setdefault(new_id, []) |
| 90 | + return new_id |
| 91 | + |
| 92 | + |
| 93 | +def _widget_meta() -> Dict[str, Any]: |
| 94 | + return { |
| 95 | + "openai/outputTemplate": WIDGET_TEMPLATE_URI, |
| 96 | + "openai/toolInvocation/invoking": WIDGET_INVOKING, |
| 97 | + "openai/toolInvocation/invoked": WIDGET_INVOKED, |
| 98 | + "openai/widgetAccessible": True, |
| 99 | + } |
| 100 | + |
| 101 | + |
| 102 | +@mcp._mcp_server.list_tools() |
| 103 | +async def _list_tools() -> List[types.Tool]: |
| 104 | + return [ |
| 105 | + types.Tool( |
| 106 | + name=TOOL_NAME, |
| 107 | + title="Add items to cart", |
| 108 | + description="Adds the provided items to the active cart and returns its state.", |
| 109 | + inputSchema=TOOL_INPUT_SCHEMA, |
| 110 | + _meta=_widget_meta(), |
| 111 | + ) |
| 112 | + ] |
| 113 | + |
| 114 | + |
| 115 | +@mcp._mcp_server.list_resources() |
| 116 | +async def _list_resources() -> List[types.Resource]: |
| 117 | + return [ |
| 118 | + types.Resource( |
| 119 | + name=WIDGET_TITLE, |
| 120 | + title=WIDGET_TITLE, |
| 121 | + uri=WIDGET_TEMPLATE_URI, |
| 122 | + description="Markup for the shopping cart widget.", |
| 123 | + mimeType=MIME_TYPE, |
| 124 | + _meta=_widget_meta(), |
| 125 | + ) |
| 126 | + ] |
| 127 | + |
| 128 | + |
| 129 | +async def _handle_read_resource(req: types.ReadResourceRequest) -> types.ServerResult: |
| 130 | + if str(req.params.uri) != WIDGET_TEMPLATE_URI: |
| 131 | + return types.ServerResult( |
| 132 | + types.ReadResourceResult( |
| 133 | + contents=[], |
| 134 | + _meta={"error": f"Unknown resource: {req.params.uri}"}, |
| 135 | + ) |
| 136 | + ) |
| 137 | + |
| 138 | + contents = [ |
| 139 | + types.TextResourceContents( |
| 140 | + uri=WIDGET_TEMPLATE_URI, |
| 141 | + mimeType=MIME_TYPE, |
| 142 | + text=SHOPPING_CART_HTML, |
| 143 | + _meta=_widget_meta(), |
| 144 | + ) |
| 145 | + ] |
| 146 | + return types.ServerResult(types.ReadResourceResult(contents=contents)) |
| 147 | + |
| 148 | + |
| 149 | +async def _handle_call_tool(req: types.CallToolRequest) -> types.ServerResult: |
| 150 | + if req.params.name != TOOL_NAME: |
| 151 | + return types.ServerResult( |
| 152 | + types.CallToolResult( |
| 153 | + content=[ |
| 154 | + types.TextContent( |
| 155 | + type="text", |
| 156 | + text=f"Unknown tool: {req.params.name}", |
| 157 | + ) |
| 158 | + ], |
| 159 | + isError=True, |
| 160 | + ) |
| 161 | + ) |
| 162 | + |
| 163 | + try: |
| 164 | + payload = AddToCartInput.model_validate(req.params.arguments or {}) |
| 165 | + except ValidationError as exc: |
| 166 | + return types.ServerResult( |
| 167 | + types.CallToolResult( |
| 168 | + content=[ |
| 169 | + types.TextContent( |
| 170 | + type="text", text=f"Invalid input: {exc.errors()}" |
| 171 | + ) |
| 172 | + ], |
| 173 | + isError=True, |
| 174 | + ) |
| 175 | + ) |
| 176 | + |
| 177 | + cart_id = _get_or_create_cart(payload.cart_id) |
| 178 | + # cart_items = carts[cart_id] |
| 179 | + cart_items = [] |
| 180 | + for item in payload.items: |
| 181 | + cart_items.append(_serialize_item(item)) |
| 182 | + |
| 183 | + structured_content = { |
| 184 | + "cartId": cart_id, |
| 185 | + "items": [dict(item) for item in cart_items], |
| 186 | + } |
| 187 | + meta = _widget_meta() |
| 188 | + meta["openai/widgetSessionId"] = cart_id |
| 189 | + |
| 190 | + message = f"Cart {cart_id} now has {len(cart_items)} item(s)." |
| 191 | + return types.ServerResult( |
| 192 | + types.CallToolResult( |
| 193 | + content=[types.TextContent(type="text", text=message)], |
| 194 | + structuredContent=structured_content, |
| 195 | + _meta=meta, |
| 196 | + ) |
| 197 | + ) |
| 198 | + |
| 199 | + |
| 200 | +mcp._mcp_server.request_handlers[types.CallToolRequest] = _handle_call_tool |
| 201 | +mcp._mcp_server.request_handlers[types.ReadResourceRequest] = _handle_read_resource |
| 202 | + |
| 203 | +app = mcp.streamable_http_app() |
| 204 | + |
| 205 | +try: |
| 206 | + from starlette.middleware.cors import CORSMiddleware |
| 207 | + |
| 208 | + app.add_middleware( |
| 209 | + CORSMiddleware, |
| 210 | + allow_origins=["*"], |
| 211 | + allow_methods=["*"], |
| 212 | + allow_headers=["*"], |
| 213 | + allow_credentials=False, |
| 214 | + ) |
| 215 | +except Exception: |
| 216 | + pass |
| 217 | + |
| 218 | + |
| 219 | +if __name__ == "__main__": |
| 220 | + import uvicorn |
| 221 | + |
| 222 | + uvicorn.run(app, host="0.0.0.0", port=8000) |
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