"""
src/parseability.py — ATS parseability verifier for generated résumés.

Simulates what an ATS parser does to a résumé and reports structural issues that
cause rejection BEFORE keyword scoring begins (the higher-signal round-one lever
from the ATS research). Advisory/non-blocking: any exception returns pass=True so
generation is never blocked by a verifier bug.

Input modes:
  - LaTeX source string (default — V2 has the .tex before compiling)
  - PDF file path string (is_pdf_path=True for the compiled artifact)

Returns: {"pass": bool, "issues": [str], "checks": {...}}.
Blocking checks: text_extractable, section_headers_present, contact_info_present.
Non-blocking (warning only): dates_present, name_present, single_column_likely.
"""
from __future__ import annotations

import re
import logging
from typing import Any

log = logging.getLogger(__name__)

_SECTION_HEADERS: dict = {
    "experience": re.compile(r"\bexperience\b", re.I),
    "education":  re.compile(r"\beducation\b", re.I),
    "skills":     re.compile(r"\b(skills|competencies)\b", re.I),
    "summary":    re.compile(r"\b(summary|profile|objective)\b", re.I),
}
_EMAIL_RE = re.compile(r"[\w.+\-]+@[\w\-]+\.[a-zA-Z]{2,}")
_PHONE_RE = re.compile(r"\+?[0-9][\d\s\-().]{8,}")
_YEAR_RE = re.compile(r"\b(19|20)\d{2}\b")
_NAME_RE = re.compile(r"^[ \t]*([A-Z][a-z]+(?:\s+[A-Z][a-z]+)+)", re.MULTILINE)


def _latex_to_plain(tex_src: str) -> str:
    try:
        from src.latex_resume import latex_to_text
        return latex_to_text(tex_src)
    except Exception:
        pass
    try:
        text = re.sub(r"\\[a-zA-Z]+\*?\{([^}]*)\}", r"\1", tex_src)
        text = re.sub(r"\\[a-zA-Z]+\*?", " ", text)
        return re.sub(r"[{}]", " ", text)
    except Exception:
        return ""


def _check_text_extractable(text: str) -> tuple:
    ok = len(text.strip()) >= 200
    return ok, None if ok else "text_not_extractable: <200 chars extracted"


def _check_contact_info(text: str) -> tuple:
    has_email = bool(_EMAIL_RE.search(text))
    has_phone = bool(_PHONE_RE.search(text))
    if has_email and has_phone:
        return True, None
    missing = ([] if has_email else ["email"]) + ([] if has_phone else ["phone"])
    return False, f"contact_info_missing:{'+'.join(missing)}"


def _check_section_headers(text: str) -> tuple:
    found = [k for k, pat in _SECTION_HEADERS.items() if pat.search(text)]
    if len(found) >= 3:
        return True, None
    missing = [k for k in _SECTION_HEADERS if k not in found]
    return False, f"missing_section_headers:{','.join(missing)}"


def _check_dates(text: str) -> tuple:
    ok = bool(_YEAR_RE.search(text))
    return ok, None if ok else "no_year_dates_found"


def _check_name(text: str) -> tuple:
    ok = bool(_NAME_RE.search(text))
    return ok, None if ok else "name_not_detected_at_top"


def _check_single_column_pdf(pdf_path: str) -> tuple:
    """Detect a genuine TWO-COLUMN layout. A single-column résumé with right-aligned
    dates and a full-width header has a wide x-spread but FEW words in the right half;
    a true two-column layout has a substantial cluster of line-START words in the right
    half. We flag only the latter (so right-aligned dates don't false-positive)."""
    try:
        import pdfplumber
        with pdfplumber.open(pdf_path) as pdf:
            if not pdf.pages:
                return None, None
            page = pdf.pages[0]
            words = page.extract_words()
            if not words or not page.width:
                return None, None
            mid = page.width / 2.0
            right_starts = sum(1 for w in words if w["x0"] > mid)
            frac = right_starts / len(words)
            # >35% of words STARTING in the right half ⇒ a real second column.
            ok = frac <= 0.35
            return ok, None if ok else f"possible_multi_column_layout:{frac:.0%}_words_right"
    except Exception as exc:
        log.debug("pdfplumber column check failed (non-fatal): %s", exc)
        return None, None


def parseability_report(source: str, is_pdf_path: bool = False) -> dict:
    """Simulate ATS parsing on a résumé. Returns {pass, issues, checks}.
    Never raises — any exception returns {pass: True, issues: [], checks: {}}."""
    try:
        checks: dict = {
            "text_extractable": False, "contact_info_present": False,
            "section_headers_present": False, "dates_present": False,
            "single_column_likely": None, "name_present": False,
        }
        issues: list = []

        if is_pdf_path:
            try:
                import pdfplumber
                with pdfplumber.open(source) as pdf:
                    text = "\n".join(p.extract_text() or "" for p in pdf.pages)
            except Exception as exc:
                log.debug("pdfplumber extraction failed: %s", exc)
                text = ""
        else:
            text = _latex_to_plain(source)

        for key, fn in (("text_extractable", _check_text_extractable),
                        ("contact_info_present", _check_contact_info),
                        ("section_headers_present", _check_section_headers),
                        ("dates_present", _check_dates),
                        ("name_present", _check_name)):
            ok, iss = fn(text)
            checks[key] = ok
            if iss:
                issues.append(iss)

        if is_pdf_path:
            ok_col, iss_col = _check_single_column_pdf(source)
            checks["single_column_likely"] = ok_col
            if iss_col:
                issues.append(iss_col)

        passed = bool(checks["text_extractable"] and checks["section_headers_present"]
                      and checks["contact_info_present"])
        return {"pass": passed, "issues": issues, "checks": checks}
    except Exception as exc:
        log.warning("parseability_report failed (non-fatal, pass=True): %s", exc)
        return {"pass": True, "issues": [], "checks": {}}