"""APIClient - Agent — HTTP client engine."""
import re
import base64
from copy import deepcopy

import httpx

from app.models import HttpRequest, HttpResponse


def resolve_variables(text: str, variables: dict) -> str:
    """Replace {{variable}} placeholders with environment values."""
    if not text or not variables:
        return text

    def replacer(m):
        key = m.group(1).strip()
        return str(variables.get(key, m.group(0)))

    return re.sub(r"\{\{(.+?)\}\}", replacer, text)


def apply_variables(req: HttpRequest, variables: dict) -> HttpRequest:
    """Return a deep copy of the request with all variables resolved."""
    r = deepcopy(req)
    r.url     = resolve_variables(r.url, variables)
    r.body    = resolve_variables(r.body, variables)
    r.headers = {k: resolve_variables(v, variables) for k, v in r.headers.items()}
    r.params  = {k: resolve_variables(v, variables) for k, v in r.params.items()}
    if r.auth_data:
        r.auth_data = {k: resolve_variables(str(v), variables) for k, v in r.auth_data.items()}
    return r


def _build_auth_headers(req: HttpRequest) -> dict:
    headers = {}
    if req.auth_type == "bearer":
        token = req.auth_data.get("token", "")
        if token:
            headers["Authorization"] = f"Bearer {token}"
    elif req.auth_type == "basic":
        user = req.auth_data.get("username", "")
        pwd  = req.auth_data.get("password", "")
        encoded = base64.b64encode(f"{user}:{pwd}".encode()).decode()
        headers["Authorization"] = f"Basic {encoded}"
    elif req.auth_type == "apikey":
        key      = req.auth_data.get("key", "")
        value    = req.auth_data.get("value", "")
        location = req.auth_data.get("in", "header")
        if location == "header" and key:
            headers[key] = value
    return headers


def send_request(req: HttpRequest, variables: dict = None) -> HttpResponse:
    r = req  # will be overwritten with resolved copy; kept here for exception handlers
    try:
        r = apply_variables(req, variables or {})

        # Check for unresolved variables
        unresolved = re.findall(r"\{\{(.+?)\}\}", r.url)
        if unresolved:
            return HttpResponse(
                error=f"Unresolved variable(s): {', '.join(unresolved)}. "
                      "Go to Tools → Environments to define them."
            )

        headers = {**r.headers, **_build_auth_headers(r)}

        # Query params (merge URL params dict + API-key-in-query)
        params = r.params.copy()
        if r.auth_type == "apikey" and r.auth_data.get("in") == "query":
            params[r.auth_data.get("key", "")] = r.auth_data.get("value", "")

        # Build request body
        content = None
        data    = None
        files   = None

        if r.body_type == "raw" and r.body:
            content = r.body.encode()
            # Auto Content-Type: honour explicit override, then try to detect JSON
            if r.content_type:
                headers.setdefault("Content-Type", r.content_type)
            elif "Content-Type" not in headers:
                stripped = r.body.lstrip()
                if stripped.startswith(("{", "[")):
                    headers["Content-Type"] = "application/json"
                else:
                    headers["Content-Type"] = "text/plain"

        elif r.body_type == "urlencoded" and r.body:
            pairs = {}
            for line in r.body.splitlines():
                if "=" in line:
                    k, _, v = line.partition("=")
                    pairs[k.strip()] = v.strip()
            data = pairs

        elif r.body_type == "form-data" and r.body:
            # Expect "key=value" lines; values starting with "@" treated as file paths
            pairs = {}
            for line in r.body.splitlines():
                if "=" in line:
                    k, _, v = line.partition("=")
                    pairs[k.strip()] = v.strip()
            data = pairs

        timeout = httpx.Timeout(
            connect=10.0,
            read=float(r.timeout),
            write=float(r.timeout),
            pool=5.0,
        )

        with httpx.Client(
            follow_redirects=True,
            timeout=timeout,
            verify=r.ssl_verify,
        ) as client:
            response = client.request(
                method=r.method,
                url=r.url,
                headers=headers,
                params=params or None,
                content=content,
                data=data,
                files=files,
            )
            body        = response.text
            size_bytes  = len(response.content)
            return HttpResponse(
                status=response.status_code,
                reason=response.reason_phrase,
                headers=dict(response.headers),
                body=body,
                elapsed_ms=response.elapsed.total_seconds() * 1000,
                size_bytes=size_bytes,
            )

    except httpx.InvalidURL:
        return HttpResponse(error=f"Invalid URL: {r.url}")
    except httpx.ConnectError as e:
        detail = str(e)
        if "CERTIFICATE_VERIFY_FAILED" in detail or "certificate" in detail.lower() or "SSL" in detail:
            return HttpResponse(error=(
                f"SSL certificate error — could not connect to {r.url}\n\n"
                f"The server's certificate is not trusted or doesn't match the hostname.\n"
                f"Tip: disable SSL verification in the request Settings tab."
            ))
        return HttpResponse(error=f"Connection refused — could not reach {r.url}")
    except httpx.ConnectTimeout:
        return HttpResponse(error=f"Connection timed out after {req.timeout}s")
    except httpx.ReadTimeout:
        return HttpResponse(error=f"Read timed out — server took too long to respond")
    except httpx.SSLError as e:
        return HttpResponse(error=f"SSL error: {e}. Disable SSL verification if using a self-signed cert.")
    except httpx.TooManyRedirects:
        return HttpResponse(error="Too many redirects — possible redirect loop")
    except Exception as e:
        return HttpResponse(error=str(e))