"""Stage 3: Dequote.

Strip quoted-reply chains, signature blocks, and disclaimer footers.
This is the unglamorous-but-critical step — without it, every email
looks like every other email and downstream clustering is destroyed.

Strategy stack (apply in order, keep all matches conservative):

1. Marker patterns (English + Chinese reply/forward markers)
2. Outlook-style block headers
3. RFC quoted lines (`> ...`)
4. Signature separator (`-- \n`)
5. Trailing-block heuristic (phone/title patterns)
6. Disclaimer footer regex

Result: only the new content the sender wrote in this message.
"""

from __future__ import annotations

import re
from dataclasses import dataclass


# --- Marker patterns ---------------------------------------------------------

_MARKERS = [
    # English: "On Mon, Apr 22, 2024 at 9:14 AM Wang <wang@us.com> wrote:"
    re.compile(r"^On\s.+?wrote:\s*$", re.MULTILINE),
    # English forwards
    re.compile(r"^[-]+\s*Forwarded message\s*[-]+\s*$", re.MULTILINE | re.IGNORECASE),
    re.compile(r"^[-]+\s*Original Message\s*[-]+\s*$", re.MULTILINE | re.IGNORECASE),
    # Chinese: "王 于 2026年4月22日 下午2:30 写道：" / variants
    re.compile(r"^.*?于\s*\d{4}年.+?写道[:：]\s*$", re.MULTILINE),
    re.compile(r"^.+?写道[:：]\s*$", re.MULTILINE),
    # Chinese forward markers
    re.compile(r"^[-]+\s*转发(的)?邮件\s*[-]+\s*$", re.MULTILINE),
    re.compile(r"^[-]+\s*原始邮件\s*[-]+\s*$", re.MULTILINE),
    # Outlook block (From: / Sent: / To: / Subject: stack)
    re.compile(
        r"^From:.+?\n(Sent|发送时间):.+?\n(To|收件人):.+?\n(Subject|主题):.+?$",
        re.MULTILINE | re.DOTALL,
    ),
    re.compile(
        r"^发件人[:：].+?\n发送时间[:：].+?\n收件人[:：].+?\n主题[:：].+?$",
        re.MULTILINE | re.DOTALL,
    ),
]

_QUOTE_LINE = re.compile(r"^\s*>+\s?", re.MULTILINE)
_SIGNATURE_SEP = re.compile(r"^--\s*$", re.MULTILINE)

_DISCLAIMER_PATTERNS = [
    re.compile(r"本邮件(及其附件)?(包含|含有)?(保密|机密).*", re.IGNORECASE | re.DOTALL),
    re.compile(r"This\s+e?-?mail.*confidential.*", re.IGNORECASE | re.DOTALL),
    re.compile(r"DISCLAIMER:.*", re.IGNORECASE | re.DOTALL),
]


@dataclass
class DequoteResult:
    text_clean: str
    strategies_used: list[str]
    chars_stripped: int


def _strip_at_first_marker(text: str, used: list[str]) -> str:
    earliest_idx: int | None = None
    matched_pattern: str | None = None
    for pat in _MARKERS:
        m = pat.search(text)
        if m and (earliest_idx is None or m.start() < earliest_idx):
            earliest_idx = m.start()
            matched_pattern = pat.pattern[:40]
    if earliest_idx is not None:
        used.append(f"marker:{matched_pattern}")
        return text[:earliest_idx].rstrip()
    return text


def _strip_quoted_lines(text: str, used: list[str]) -> str:
    """Cut all leading-`>` lines AND any trailing blocks of them."""
    if not _QUOTE_LINE.search(text):
        return text
    used.append("rfc_quoted_lines")
    lines = text.splitlines()
    # Find first line that is NOT a quoted line, working from the bottom up
    while lines and (
        _QUOTE_LINE.match(lines[-1])
        or lines[-1].strip() == ""
    ):
        lines.pop()
    cleaned = [ln for ln in lines if not _QUOTE_LINE.match(ln)]
    return "\n".join(cleaned).strip()


def _strip_signature(text: str, used: list[str]) -> str:
    m = _SIGNATURE_SEP.search(text)
    if m:
        used.append("signature_sep_dashdash")
        return text[: m.start()].rstrip()
    return text


def _strip_trailing_block_heuristic(text: str, used: list[str]) -> str:
    """If the last 3-8 lines look like a contact block, drop them.

    Heuristic: trailing block of short lines that contains a phone number
    pattern, an email, or a generic title word like 'CEO/总监/经理/董事长'.
    """
    lines = text.splitlines()
    if len(lines) < 6:
        return text
    tail = [ln for ln in lines[-8:] if ln.strip()]
    if len(tail) < 2 or len(tail) > 8:
        return text
    joined = "\n".join(tail)
    has_signal = (
        re.search(r"\+?\d[\d\s\-()]{6,}", joined)
        or re.search(r"[\w.+-]+@[\w-]+\.[\w.-]+", joined)
        or re.search(r"(CEO|CTO|CFO|总监|经理|董事长|总裁|主管|VP|Director)", joined)
    )
    if not has_signal:
        return text
    avg_len = sum(len(t) for t in tail) / len(tail)
    if avg_len > 60:  # too long, probably real content
        return text
    used.append("trailing_block_heuristic")
    cut_idx = len(lines)
    for i in range(len(lines) - 1, -1, -1):
        if lines[i].strip() == "" and i < len(lines) - 1:
            continue
        if lines[i] in tail:
            cut_idx = i
        else:
            break
    return "\n".join(lines[:cut_idx]).rstrip()


def _strip_disclaimer(text: str, used: list[str]) -> str:
    for pat in _DISCLAIMER_PATTERNS:
        m = pat.search(text)
        if m:
            used.append(f"disclaimer:{pat.pattern[:30]}")
            text = text[: m.start()].rstrip()
    return text


def dequote(text: str) -> DequoteResult:
    """Run the full dequote stack and return the cleaned text."""
    if not text:
        return DequoteResult(text_clean="", strategies_used=[], chars_stripped=0)
    original_len = len(text)
    used: list[str] = []
    text = _strip_at_first_marker(text, used)
    text = _strip_quoted_lines(text, used)
    text = _strip_signature(text, used)
    text = _strip_disclaimer(text, used)
    text = _strip_trailing_block_heuristic(text, used)
    return DequoteResult(
        text_clean=text.strip(),
        strategies_used=used,
        chars_stripped=original_len - len(text.strip()),
    )