from __future__ import annotations

import os
import re
from typing import Any
from urllib.parse import urlsplit

import httpx
from fastapi import APIRouter, HTTPException
from pydantic import BaseModel, ConfigDict, Field, field_validator

router = APIRouter(prefix="/v1/sms", tags=["sms"])
_PHONE_RE = re.compile(r"^\+[1-9][0-9]{7,14}$")
_MAX_CONTENT_LENGTH = 1600
_DEFAULT_BASE_URL = "https://api.httpsms.com"


class SendSMSRequest(BaseModel):
    model_config = ConfigDict(populate_by_name=True, extra="forbid")
    from_number: str = Field(alias="from", min_length=9, max_length=16)
    to: str = Field(min_length=9, max_length=16)
    content: str = Field(min_length=1, max_length=_MAX_CONTENT_LENGTH)

    @field_validator("from_number", "to")
    @classmethod
    def validate_phone_number(cls, value: str) -> str:
        value = value.strip()
        if not _PHONE_RE.fullmatch(value):
            raise ValueError("Phone numbers must use international E.164 format, e.g. +2348012345678")
        return value

    @field_validator("content")
    @classmethod
    def validate_content(cls, value: str) -> str:
        value = value.strip()
        if not value:
            raise ValueError("SMS content must not be blank")
        if any(ord(char) < 32 and char not in "\n\r\t" for char in value):
            raise ValueError("SMS content contains unsupported control characters")
        return value


def _configuration() -> tuple[str, str]:
    api_key = os.getenv("HTTPSMS_API_KEY", "").strip()
    if not api_key:
        raise HTTPException(status_code=503, detail="httpSMS integration is not configured")
    base_url = os.getenv("HTTPSMS_API_BASE_URL", _DEFAULT_BASE_URL).strip().rstrip("/")
    parsed = urlsplit(base_url)
    if (
        parsed.scheme != "https"
        or not parsed.hostname
        or parsed.username is not None
        or parsed.password is not None
        or parsed.query
        or parsed.fragment
    ):
        raise HTTPException(status_code=503, detail="httpSMS base URL configuration is invalid")
    return base_url, api_key


@router.post("/send")
async def send_sms(payload: SendSMSRequest) -> dict[str, Any]:
    """Send an SMS through the configured httpSMS API."""
    base_url, api_key = _configuration()
    request_body = {"from": payload.from_number, "to": payload.to, "content": payload.content}
    try:
        async with httpx.AsyncClient(
            timeout=httpx.Timeout(20.0, connect=5.0), follow_redirects=False
        ) as client:
            response = await client.post(
                f"{base_url}/v1/messages/send",
                headers={"x-api-key": api_key, "Content-Type": "application/json"},
                json=request_body,
            )
    except httpx.TimeoutException as exc:
        raise HTTPException(status_code=504, detail="httpSMS request timed out") from exc
    except httpx.RequestError as exc:
        raise HTTPException(status_code=502, detail="Unable to reach the httpSMS API") from exc
    if not 200 <= response.status_code < 300:
        raise HTTPException(
            status_code=502,
            detail=f"httpSMS rejected the request (upstream status {response.status_code})",
        )
    try:
        upstream: Any = response.json()
    except ValueError:
        upstream = {"message": response.text[:500]} if response.text else {}
    return {"success": True, "upstream_status": response.status_code, "result": upstream}