"""
Parse the candidate's original resume PDF into the canonical Resume model.

This is run ONCE at startup (cached to disk) and used as the base for every
LLM tailoring call in Phase 4.

The parser is intentionally forgiving: it joins multi-line bullets, strips
sub-section headers (NIAT Revamp, AI Chatbot, etc.) into flat bullets,
and limits to ~8 bullets per role (keeps the prompt tight). The LLM picks
the best ones per JD.
"""

from __future__ import annotations
import os
import re
import json
import pdfplumber

from .resume_model import Resume, Role, Education, Contact
from .resume_customizer import (
    _extract_candidate_name, _normalize_spaced_text, _read_docx_text,
)

try:
    from config import CONTACT_LOCATION
except Exception:  # pragma: no cover - config always present in app runtime
    CONTACT_LOCATION = "Hyderabad, Telangana, India · Open to relocate"


_DATE_PATTERN = re.compile(
    r"(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\w*\s+\d{4}\s*[-–—to]+\s*"
    r"(?:(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\w*\s*\n?\s*\d{4}|Present|Current|Now)",
    re.IGNORECASE,
)
_PARTIAL_DATE_RE = re.compile(
    r"(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\w*"
    r"(?:\s+\d{2,4})?"
    r"(?:\s*[-–—to]+\s*"
        r"(?:(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\w*"
        r"(?:\s+\d{2,4})?"
        r"|\d{2,4}|Present|Current|Now)"
    r")?",
    re.IGNORECASE,
)


def parse_resume_pdf(pdf_path: str) -> Resume:
    """Read the PDF and return a Resume canonical model."""
    raw_text = ""
    with pdfplumber.open(pdf_path) as pdf:
        for page in pdf.pages:
            t = page.extract_text()
            if t:
                raw_text += t + "\n"

    name = _extract_candidate_name(raw_text)
    contact = _extract_contact(raw_text)
    summary = _extract_summary(raw_text)
    roles = _extract_roles(raw_text)
    achievements = _extract_achievements(raw_text)
    education = _extract_education_entries(raw_text)

    return Resume(
        name=name,
        contact=contact,
        summary=summary,
        roles=roles,
        achievements=achievements,
        education=education,
    )


def parse_resume_pdf_cached(pdf_path: str, cache_path: str = "data/resume/_parsed.json") -> Resume:
    """Parse with disk cache keyed by PDF mtime + size."""
    if not os.path.exists(pdf_path):
        raise FileNotFoundError(pdf_path)
    stat = os.stat(pdf_path)
    # cache version bumped to v2 when the contact `location` field was added, so
    # pre-existing caches (without an address) are rebuilt.
    cache_key = f"v2_{stat.st_mtime_ns}_{stat.st_size}"

    if os.path.exists(cache_path):
        try:
            with open(cache_path, encoding="utf-8") as f:
                cached = json.load(f)
            if cached.get("_cache_key") == cache_key:
                resume = Resume.from_dict(cached["resume"])
                if not resume.contact.location:
                    resume.contact.location = CONTACT_LOCATION
                return resume
        except Exception:
            pass  # Cache invalid, re-parse

    resume = parse_resume_pdf(pdf_path)
    os.makedirs(os.path.dirname(cache_path), exist_ok=True)
    with open(cache_path, "w", encoding="utf-8") as f:
        json.dump({"_cache_key": cache_key, "resume": resume.to_dict()}, f,
                  ensure_ascii=False, indent=2)
    return resume


# ─────────────────────────────────────────────────────────────────────────
# Section extractors
# ─────────────────────────────────────────────────────────────────────────

def _extract_location(text: str) -> str:
    """Best-effort: find a 'City, State, Country' line near the top of the resume.

    Conservative on purpose — only accepts a short, comma-bearing header line so
    we don't mistake a sentence for an address. Returns "" when nothing matches,
    and the caller falls back to the configured CONTACT_LOCATION.
    """
    for line in text.splitlines()[:10]:
        s = line.strip().strip("|•·-").strip()
        if not (3 <= len(s) <= 60) or "," not in s:
            continue
        if re.search(r"@|https?://|linkedin\.com|\d{6,}", s, re.I):
            continue  # skip email / url / phone lines
        # India-based or a generic "City, Region(, Country)" shape
        if re.search(r"\bindia\b", s, re.I) or re.match(
            r"^[A-Z][a-zA-Z.]+(?:\s[A-Z][a-zA-Z.]+)*,\s*[A-Z][a-zA-Z.]+", s
        ):
            return s
    return ""


def _extract_contact(text: str) -> Contact:
    email_m = re.search(r"[\w.+-]+@[\w-]+\.[a-zA-Z]{2,}", text)
    phone_m = re.search(r"[\+]?[0-9]{1,4}[\s.-]?[0-9]{4,5}[\s.-]?[0-9]{4,5}", text)
    linkedin_m = re.search(r"linkedin\.com/in/[\w-]+", text, re.I)
    return Contact(
        phone=phone_m.group() if phone_m else "",
        email=email_m.group() if email_m else "",
        linkedin=("https://" + linkedin_m.group()) if linkedin_m else "",
        # Option B: use the resume's own location if present, else the
        # configured fallback so the ATS "address" check always passes.
        location=_extract_location(text) or CONTACT_LOCATION,
    )


def _extract_summary(text: str) -> str:
    """Return the original Professional Summary paragraph (LLM will rewrite it)."""
    text_norm = _normalize_spaced_text(text)
    m = re.search(
        r"PROFESSIONAL\s+SUMMARY\s*\n(.*?)"
        r"(?:\n(?:PROFESSIONAL\s+EXPERIENCE|EXPERIENCE|EDUCATION|KEY\s+METRICS|"
        r"CORE\s+COMPETENCIES|SKILLS|PROJECTS)|\Z)",
        text_norm, re.DOTALL,
    )
    if not m:
        return ""
    body = m.group(1).strip()
    # Collapse multi-line summary into one paragraph
    return re.sub(r"\s+", " ", body)


def _extract_roles(text: str, max_bullets_per_role: int = 8) -> list[Role]:
    """
    Parse the experience section into Role entries with FLAT bullets.

    Sub-section headers (NIAT Revamp, AI Chatbot etc.) are NOT preserved —
    they're treated as transition markers and dropped. Their bullets are
    flattened into the parent role.

    Continuation lines from wrapped bullets are joined into the previous
    bullet.

    Result is capped at `max_bullets_per_role` (default 8) per role —
    the LLM will pick the best 5-7 when tailoring.
    """
    text_norm = _normalize_spaced_text(text)
    exp_match = re.search(
        r"(?:PROFESSIONAL\s+|WORK\s+)?EXPERIENCE[S]?\s*\n(.*?)"
        r"(?:\n(?:KEY\s+METRICS|KEY\s+ACHIEVEMENTS|CORE\s+COMPETENCIES|"
        r"TECHNICAL\s+SKILLS|SKILLS\s*&|SKILLS\s*\n|EDUCATION|"
        r"CERTIFICATIONS\s*\n|CERTIFICATIONS\s*&|PROJECTS\s*\n|PROJECTS\s*&|"
        r"AWARDS|LANGUAGES|REFERENCES)|\Z)",
        text_norm, re.DOTALL,
    )
    if not exp_match:
        return []

    exp_text = exp_match.group(1).strip()
    date_matches = list(_DATE_PATTERN.finditer(exp_text))
    if not date_matches:
        return []

    # Slice into blocks: one block per role
    block_starts: list[int] = []
    for dm in date_matches:
        line_start = exp_text.rfind("\n", 0, dm.start()) + 1
        block_starts.append(line_start)
    block_starts.append(len(exp_text))

    roles: list[Role] = []
    for i, dm in enumerate(date_matches):
        block = exp_text[block_starts[i]:block_starts[i + 1]]
        dates = re.sub(r"\s+", " ", dm.group()).strip()

        header_line_end = block.find("\n")
        if header_line_end == -1:
            header_line, body = block, ""
        else:
            header_line, body = block[:header_line_end], block[header_line_end + 1:]

        # Strip ANY partial date from header
        head = _PARTIAL_DATE_RE.sub("", header_line).strip(" |·.,")
        # Split: "Role · Company | Location"
        parts = re.split(r"[·•|]", head, maxsplit=1)
        title = parts[0].strip() if parts else head
        company_loc = parts[1].strip() if len(parts) > 1 else ""

        # Further split company_loc into company + location
        company, location = _split_company_location(company_loc)

        bullets = _flatten_bullets(body, max_bullets_per_role)

        roles.append(Role(
            title=title,
            company=company,
            location=location,
            dates=dates,
            bullets=bullets,
        ))

    return roles


def _split_company_location(s: str) -> tuple[str, str]:
    """
    Try to split "Company | Location" or "Company, Location" or just leave as company.
    """
    s = s.strip()
    # "Company | Location" pattern
    if "|" in s:
        parts = [p.strip() for p in s.split("|", 1)]
        return parts[0], parts[1]
    # "Company, City" pattern
    if "," in s:
        # Heuristic: split on last comma if right side looks like a location
        # (e.g. "Hyderabad, India" → keep together; "Co. Pvt. Ltd., Hyderabad" → split)
        idx = s.rfind(",")
        right = s[idx + 1:].strip()
        # Location-y words on the right side
        if any(w in right for w in ["India", "USA", "UK", "Remote", "Bengaluru",
                                     "Bangalore", "Hyderabad", "Mumbai", "Delhi",
                                     "Pune", "Chennai", "Gurgaon", "Gurugram",
                                     "Noida", "Worldwide"]):
            return s[:idx].strip(), right
    return s, ""


def _flatten_bullets(body: str, max_count: int) -> list[str]:
    """
    Walk the body lines and produce a flat list of bullets.
    - Drop sub-section headers (lines without bullet char, not Scope:)
    - Skip orphan year-only lines (date wrap artifacts)
    - Skip Scope: meta lines
    - Join continuation lines into the previous bullet
    - Cap at max_count (best ones first — the LLM picks)
    """
    bullets: list[str] = []
    for raw in body.split("\n"):
        line = raw.strip()
        if not line:
            continue
        if re.fullmatch(r"\d{4}", line):
            continue  # date wrap artifact
        low = line.lower()
        if low.startswith("scope:"):
            continue  # meta line — drop entirely in canonical model
        if line.startswith(("•", "-", "–", "—", "*", "▪", "●")):
            bullets.append(line.lstrip("•-–—*▪● ").strip())
        else:
            # Either a sub-section header OR a continuation of previous bullet.
            # Continuation if previous bullet exists AND this line is short
            # / starts lowercase / etc.
            if bullets and _is_continuation(line):
                bullets[-1] = bullets[-1] + " " + line
            # else: sub-section header — DROP (canonical model has no sub-sections)
    # Light cleanup
    cleaned = []
    for b in bullets:
        b = re.sub(r"\s+", " ", b).strip()
        b = b.rstrip(",;.")
        if b and len(b) >= 10:
            cleaned.append(b)

    return cleaned[:max_count]


def _is_continuation(line: str) -> bool:
    """Heuristic: line wraps from the previous bullet, not a new sub-section."""
    if not line:
        return False
    first = line[0]
    if first.islower() or first.isdigit():
        return True
    if first in "→+%&([{":
        return True
    # Multi-Title-Case in first 60 chars → looks like a section header
    head_60 = line[:60]
    cap_words = re.findall(r"\b[A-Z][a-z]+", head_60)
    return len(cap_words) < 2


def _extract_achievements(text: str) -> list[str]:
    """Pull a few KEY METRICS / KEY ACHIEVEMENTS bullets if present."""
    text_norm = _normalize_spaced_text(text)
    m = re.search(
        r"KEY\s+(?:METRICS|ACHIEVEMENTS)(?:\s*&\s*ACHIEVEMENTS)?\s*\n(.*?)"
        r"(?:\n(?:CORE\s+COMPETENCIES|SKILLS|EDUCATION|CERTIFICATIONS|"
        r"PROJECTS|LANGUAGES|EXPERIENCE)|\Z)",
        text_norm, re.DOTALL,
    )
    if not m:
        return []

    body = m.group(1)
    out: list[str] = []
    for raw in body.split("\n"):
        line = raw.strip().lstrip("•-–—*▪● ").strip()
        if not line:
            continue
        # Drop sub-section headers like "Funnel & Revenue"
        if not any(ch in line for ch in [" ", ":"]) and len(line) < 30:
            continue
        # Title-case headers without quantification are sub-categories
        if re.match(r"^[A-Z][A-Za-z\s&]+$", line) and "%" not in line and not re.search(r"\d", line):
            continue
        if len(line) >= 20:
            out.append(line)

    return out[:5]


def _extract_education_entries(text: str) -> list[Education]:
    """Parse EDUCATION section into structured entries."""
    text_norm = _normalize_spaced_text(text)
    m = re.search(
        r"EDUCATION(?:\s*&\s*CERTIFICATIONS?)?\s*\n(.*?)"
        r"(?:\n(?:CERTIFICATIONS\s*\n|SKILLS\s*\n|EXPERIENCE\s*\n|"
        r"PROJECTS\s*\n|REFERENCES|LANGUAGES\s*\n|CORE\s+COMPETENCIES)|\Z)",
        text_norm, re.DOTALL,
    )
    if not m:
        return []

    body = m.group(1).strip()
    entries: list[Education] = []

    # Education entries often come as: "Degree" line, "Institution" line, optionally dates
    lines = [ln.strip() for ln in body.split("\n") if ln.strip()]
    i = 0
    while i < len(lines):
        line = lines[i]
        # Try to find a date in this line or extract from the line
        date_match = _PARTIAL_DATE_RE.search(line)
        dates = date_match.group() if date_match else ""
        degree_line = _PARTIAL_DATE_RE.sub("", line).strip(" |·.,")
        # Next line may be the institution (heuristic: short title-case line)
        institution = ""
        if i + 1 < len(lines):
            next_line = lines[i + 1]
            next_date = _PARTIAL_DATE_RE.search(next_line)
            # If next line is just institution (no date / short)
            if not next_date and len(next_line) < 80 and not next_line.startswith(("•", "-")):
                # AND it's not another degree
                if not _looks_like_degree(next_line):
                    institution = next_line
                    i += 1
            elif next_date and len(next_line) < 100:
                # Sometimes institution + dates on same line — parse it
                institution = _PARTIAL_DATE_RE.sub("", next_line).strip(" |·.,")
                if not dates:
                    dates = next_date.group()
                i += 1

        if degree_line:
            entries.append(Education(
                degree=degree_line,
                institution=institution,
                dates=dates,
            ))
        i += 1

    return entries


def _looks_like_degree(line: str) -> bool:
    """Heuristic: does this line look like a degree title?"""
    keywords = ["diploma", "bachelor", "master", "phd", "doctor", "mba",
                "btech", "bsc", "msc", "ba ", "bs ", "ma ", "ms ", "engineering",
                "management", "computer science", "certification", "certificate"]
    low = line.lower()
    return any(k in low for k in keywords)