"""Tool code generator for classified OpenAPI endpoints.

Generates Python source code for LangChain @tool functions and
YAML agent configurations from classification results.
"""

from __future__ import annotations

import re

import yaml

from app.openapi.models import ClassificationResult, EndpointInfo, GeneratedTool, ParameterInfo

_INDENT = "    "


def generate_tool_code(classification: ClassificationResult, base_url: str) -> GeneratedTool:
    """Generate a LangChain @tool function for a classified endpoint.

    Returns a GeneratedTool with the function source code as a string.
    """
    ep = classification.endpoint
    func_name = _to_snake_case(ep.operation_id)
    params = _collect_params(ep)
    sig = _build_signature(params, ep.request_body_schema)
    docstring = ep.summary or ep.description or ep.operation_id
    interrupt_comment = _interrupt_comment(classification)
    http_call = _build_http_call(ep, base_url, params)

    lines = [
        "@tool",
        f"async def {func_name}({sig}) -> str:",
        f'{_INDENT}"""{docstring}"""',
    ]
    if interrupt_comment:
        lines.append(f"{_INDENT}{interrupt_comment}")
    lines += [
        f"{_INDENT}async with httpx.AsyncClient() as client:",
        f"{_INDENT}{_INDENT}{http_call}",
        f"{_INDENT}{_INDENT}return response.text",
    ]

    code = "\n".join(lines)
    return GeneratedTool(
        function_name=func_name,
        endpoint=ep,
        classification=classification,
        code=code,
    )


def generate_agent_yaml(
    classifications: tuple[ClassificationResult, ...],
    base_url: str,
) -> str:
    """Generate an agents.yaml string from a set of classification results.

    Groups tools by agent_group, creating one agent entry per group.
    """
    if not classifications:
        return yaml.dump({"agents": []})

    groups: dict[str, dict] = {}
    for clf in classifications:
        group = clf.agent_group
        func_name = _to_snake_case(clf.endpoint.operation_id)
        if group not in groups:
            permission = "read" if clf.access_type == "read" else "write"
            groups[group] = {
                "name": group,
                "description": f"Agent for {group} operations",
                "permission": permission,
                "tools": [],
            }
        groups[group]["tools"].append(func_name)

    return yaml.dump({"agents": list(groups.values())}, sort_keys=False)


# --- Private helpers ---


def _collect_params(ep: EndpointInfo) -> list[ParameterInfo]:
    """Return path params first, then query params."""
    path_params = [p for p in ep.parameters if p.location == "path"]
    other_params = [p for p in ep.parameters if p.location != "path"]
    return path_params + other_params


def _build_signature(params: list[ParameterInfo], body_schema: dict | None) -> str:
    """Build a Python function signature string from parameters."""
    parts: list[str] = []
    for p in params:
        py_type = _schema_type_to_python(p.schema_type)
        if p.required:
            parts.append(f"{p.name}: {py_type}")
        else:
            parts.append(f"{p.name}: {py_type} | None = None")
    if body_schema:
        parts.append("body: dict | None = None")
    return ", ".join(parts)


def _build_http_call(
    ep: EndpointInfo, base_url: str, params: list[ParameterInfo]
) -> str:
    """Build the httpx client call line."""
    method = ep.method.lower()
    path = ep.path

    # Replace path parameters with f-string expressions
    for p in params:
        if p.location == "path":
            path = path.replace(f"{{{p.name}}}", f"{{{p.name}}}")

    url_expr = f'f"{base_url}{path}"'

    query_params = [p for p in params if p.location == "query"]
    extra_args = []
    if query_params:
        qp_dict = "{" + ", ".join(f'"{p.name}": {p.name}' for p in query_params) + "}"
        extra_args.append(f"params={qp_dict}")

    if ep.request_body_schema and method in ("post", "put", "patch"):
        extra_args.append("json=body")

    args_str = ", ".join([url_expr] + extra_args)
    return f"response = await client.{method}({args_str})"


def _interrupt_comment(classification: ClassificationResult) -> str:
    """Return a comment line if the endpoint requires interrupt/approval."""
    if classification.needs_interrupt:
        return "# INTERRUPT: requires human approval before execution"
    return ""


def _schema_type_to_python(schema_type: str) -> str:
    """Map OpenAPI schema type to Python type annotation."""
    mapping = {
        "string": "str",
        "integer": "int",
        "number": "float",
        "boolean": "bool",
        "array": "list",
        "object": "dict",
    }
    return mapping.get(schema_type, "str")


def _to_snake_case(name: str) -> str:
    """Convert operationId to a valid snake_case Python identifier."""
    # Replace non-alphanumeric with underscore
    clean = re.sub(r"[^a-zA-Z0-9]+", "_", name).strip("_")
    return clean.lower()