"""Thailand external-sector / trade factor — TradingEconomics Thailand.

Source: https://tradingeconomics.com/thailand/current-account
(server-rendered HTML, same infobox/infrastructure as the auto_credit source —
the "related indicators" table lists the current value, previous value, unit
and reporting period for Thailand's external account).

Verified live: the current-account page's related-indicators table exposes
(Jul 2026) Exports 34,781.10, Imports 38,399.60, Balance of Trade -3,611.00
USD mn and (Jun 2026) Current Account -3,473.85 USD mn. Replaces the stale
BOT report-60 path (which only carried data through 2011) with a CURRENT,
free, scrapeable source per the plan's "do not ship a wrong/stale series" gate.
"""

from __future__ import annotations

import html
import re
from dataclasses import dataclass
from typing import Optional
from urllib.request import Request, urlopen

_USER_AGENT = (
    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 "
    "(KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36"
)
_URL = "https://tradingeconomics.com/thailand/current-account"


class ThaiTradeError(Exception):
    """Raised when the TradingEconomics Thailand page cannot be fetched/parsed."""


@dataclass(frozen=True)
class ThaiTradeSnapshot:
    current_account_usdm: Optional[float] = None      # USD million
    trade_balance_usdm: Optional[float] = None        # USD million
    exports_usdm: Optional[float] = None              # USD million
    imports_usdm: Optional[float] = None              # USD million
    as_of: str = ""
    source: str = "tradingeconomics.thai-trade"

    def to_dict(self) -> dict:
        return {
            "source": self.source,
            "as_of": self.as_of,
            "current_account_usdm": self.current_account_usdm,
            "trade_balance_usdm": self.trade_balance_usdm,
            "exports_usdm": self.exports_usdm,
            "imports_usdm": self.imports_usdm,
        }


def _fetch(url: str = _URL, timeout: float = 30.0) -> str:
    req = Request(url, headers={"User-Agent": _USER_AGENT, "Accept": "text/html"})
    try:
        with urlopen(req, timeout=timeout) as resp:
            raw = resp.read()
    except Exception as exc:
        raise ThaiTradeError(f"failed to fetch {url}: {exc}") from exc
    try:
        return raw.decode("utf-8")
    except UnicodeDecodeError:
        return raw.decode("latin-1", "ignore")


def _tables(html_text: str) -> list[str]:
    return re.findall(r"<table[^>]*>(.*?)</table>", html_text, re.S)


def _cells(row_html: str) -> list[str]:
    return [
        html.unescape(re.sub(r"<[^>]+>", "", td)).strip()
        for td in re.findall(r"<td[^>]*>(.*?)</td>", row_html, re.S)
        if td.strip()
    ]


def _to_float(text: str) -> Optional[float]:
    text = text.replace(",", "").strip().replace("%", "")
    if not text or text in ("-", "N/A", "…"):
        return None
    try:
        return float(text)
    except ValueError:
        return None


def parse_thai_trade_html(html_text: str) -> ThaiTradeSnapshot:
    """Parse the TradingEconomics Thailand current-account related table."""
    current = trade = exports = imports = None
    as_of = ""

    for table in _tables(html_text):
        rows = re.findall(r"<tr[^>]*>(.*?)</tr>", table, re.S)
        for row_html in rows:
            cells = _cells(row_html)
            if not cells:
                continue
            label = cells[0].strip()
            if label == "Current Account":
                current = _to_float(cells[1])
                if len(cells) > 4:
                    as_of = cells[4]
            elif label == "Balance of Trade":
                trade = _to_float(cells[1])
            elif label == "Exports" and exports is None:
                exports = _to_float(cells[1])
            elif label == "Imports" and imports is None:
                imports = _to_float(cells[1])

    if current is None and exports is None and imports is None:
        raise ThaiTradeError("no Thai trade series found in TradingEconomics page")

    return ThaiTradeSnapshot(
        current_account_usdm=current,
        trade_balance_usdm=trade,
        exports_usdm=exports,
        imports_usdm=imports,
        as_of=as_of,
    )


def fetch_thai_trade(timeout: float = 30.0) -> ThaiTradeSnapshot:
    return parse_thai_trade_html(_fetch(timeout=timeout))