"""GEDCOM import/export.

A pragmatic parser + mapper for the common subset of GEDCOM (5.5.1 / 7 share
the line grammar): INDI, FAM, SOUR. Import maps records into a tree and returns
a mapping report (counts + unmapped tags); export serializes the tree back to
GEDCOM. Runs inline for now — large files should move to the worker later.
"""

import re
import uuid
from collections import defaultdict
from datetime import date

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from app.models.enums import ParentChildQualifier, RelationshipType
from app.models.event import Event
from app.models.person import Name, Person
from app.models.place import Place
from app.models.relationship import Relationship
from app.models.source import Citation, Source
from app.models.tree import Tree
from app.models.user import User
from app.services import privacy
from app.services.audit import record_audit
from app.services.exceptions import Forbidden

# GEDCOM event tag -> our event_type (INDI-level).
INDI_EVENTS = {
    "BIRT": "birth", "DEAT": "death", "BAPM": "baptism", "CHR": "christening",
    "BURI": "burial", "CREM": "cremation", "RESI": "residence", "CENS": "census",
    "IMMI": "immigration", "EMIG": "emigration", "OCCU": "occupation",
    "EDUC": "education", "GRAD": "graduation", "RETI": "retirement",
    "NATU": "naturalization", "BAPL": "baptism",
}
# FAM-level events.
FAM_EVENTS = {"MARR": "marriage", "DIV": "divorce", "ENGA": "engagement"}
EVENT_TO_GED = {v: k for k, v in {**INDI_EVENTS, **FAM_EVENTS}.items()}


class GedcomNode:
    __slots__ = ("level", "tag", "value", "xref", "children")

    def __init__(self, level: int, tag: str, value: str = "", xref: str | None = None):
        self.level = level
        self.tag = tag
        self.value = value
        self.xref = xref
        self.children: list[GedcomNode] = []

    def first(self, tag: str) -> "GedcomNode | None":
        return next((c for c in self.children if c.tag == tag), None)

    def all(self, tag: str) -> list["GedcomNode"]:
        return [c for c in self.children if c.tag == tag]

    def text(self, tag: str, default: str | None = None) -> str | None:
        n = self.first(tag)
        return n.value if n is not None else default


def parse_records(text: str) -> list[GedcomNode]:
    roots: list[GedcomNode] = []
    stack: list[GedcomNode] = []
    for raw in text.replace("\r\n", "\n").replace("\r", "\n").split("\n"):
        line = raw.lstrip("").rstrip()
        if not line.strip():
            continue
        parts = line.split(" ", 1)
        try:
            level = int(parts[0])
        except ValueError:
            continue
        rest = parts[1] if len(parts) > 1 else ""
        xref: str | None = None
        if rest.startswith("@"):
            end = rest.find("@", 1)
            if end != -1:
                xref = rest[: end + 1]
                rest = rest[end + 1:].strip()
        tparts = rest.split(" ", 1)
        tag = tparts[0]
        value = tparts[1] if len(tparts) > 1 else ""

        while stack and stack[-1].level >= level:
            stack.pop()
        parent = stack[-1] if stack else None

        if tag in ("CONC", "CONT") and parent is not None:
            parent.value += ("" if tag == "CONC" else "\n") + value
            continue

        node = GedcomNode(level, tag, value, xref)
        if parent is None:
            roots.append(node)
        else:
            parent.children.append(node)
        stack.append(node)
    return roots


def _parse_name(value: str) -> tuple[str | None, str | None]:
    if "/" in value:
        given, _, rest = value.partition("/")
        surname = rest.split("/", 1)[0]
        return given.strip() or None, surname.strip() or None
    return value.strip() or None, None


def _year(date_value: str | None) -> str | None:
    if not date_value:
        return None
    m = re.search(r"\b(\d{3,4})\b", date_value)
    return m.group(1) if m else None


def _date_start(date_value: str | None) -> date | None:
    y = _year(date_value)
    if not y:
        return None
    try:
        return date(int(y), 1, 1)
    except ValueError:
        return None


def _sex(value: str | None) -> str | None:
    if not value:
        return None
    v = value.strip().upper()
    return {"M": "male", "F": "female"}.get(v, value.strip().lower() or None)


async def import_gedcom(
    session: AsyncSession, *, actor: User, tree: Tree, text: str
) -> dict:
    if not await privacy.can_edit_tree(session, user_id=actor.id, tree=tree):
        raise Forbidden("not an editor of this tree")

    roots = parse_records(text)
    counts = defaultdict(int)
    unmapped: set[str] = set()
    place_cache: dict[str, uuid.UUID] = {}
    source_map: dict[str, uuid.UUID] = {}
    person_map: dict[str, uuid.UUID] = {}

    async def place_id(name: str | None) -> uuid.UUID | None:
        if not name:
            return None
        if name in place_cache:
            return place_cache[name]
        p = Place(tree_id=tree.id, name=name)
        session.add(p)
        await session.flush()
        place_cache[name] = p.id
        counts["places"] += 1
        return p.id

    # Sources first (so citations can reference them).
    for rec in roots:
        if rec.tag == "SOUR" and rec.xref:
            src = Source(
                tree_id=tree.id,
                title=rec.text("TITL") or rec.text("ABBR") or "Untitled source",
                author=rec.text("AUTH"),
                publication_info=rec.text("PUBL"),
                citation_text=rec.text("TEXT"),
            )
            session.add(src)
            await session.flush()
            source_map[rec.xref] = src.id
            counts["sources"] += 1

    async def add_citations(holder: GedcomNode, **target) -> None:
        for s in holder.all("SOUR"):
            sid = source_map.get(s.value.strip())
            if sid is None:
                continue
            session.add(
                Citation(tree_id=tree.id, source_id=sid, page=s.text("PAGE"), **target)
            )
            counts["citations"] += 1

    # Individuals.
    for rec in roots:
        if rec.tag != "INDI" or not rec.xref:
            continue
        person = Person(tree_id=tree.id, gender=_sex(rec.text("SEX")))
        session.add(person)
        await session.flush()
        person_map[rec.xref] = person.id
        counts["persons"] += 1

        for i, nm in enumerate(rec.all("NAME")):
            given, surname = _parse_name(nm.value)
            session.add(
                Name(
                    tree_id=tree.id,
                    person_id=person.id,
                    name_type="birth",
                    given=given,
                    surname=surname,
                    display_name=nm.value or None,
                    is_primary=(i == 0),
                    sort_order=i,
                )
            )
            counts["names"] += 1

        await add_citations(rec, person_id=person.id)

        for child in rec.children:
            if child.tag in INDI_EVENTS:
                dv = child.text("DATE")
                ev = Event(
                    tree_id=tree.id,
                    person_id=person.id,
                    event_type=INDI_EVENTS[child.tag],
                    date_value=dv,
                    date_start=_date_start(dv),
                    place_id=await place_id(child.text("PLAC")),
                )
                session.add(ev)
                await session.flush()
                counts["events"] += 1
                await add_citations(child, event_id=ev.id)
            elif child.tag in ("NAME", "SEX", "SOUR", "FAMC", "FAMS", "CHAN", "OBJE", "_UID"):
                continue
            else:
                unmapped.add(child.tag)

    # Families -> partnerships, parent-child edges, marriage events.
    for rec in roots:
        if rec.tag != "FAM":
            continue
        counts["families"] += 1
        husb = person_map.get((rec.text("HUSB") or "").strip())
        wife = person_map.get((rec.text("WIFE") or "").strip())
        partnership_id: uuid.UUID | None = None
        if husb and wife:
            rel = Relationship(
                tree_id=tree.id,
                type=RelationshipType.partnership,
                person_from_id=husb,
                person_to_id=wife,
            )
            session.add(rel)
            await session.flush()
            partnership_id = rel.id
            counts["relationships"] += 1

        for fe in rec.children:
            if fe.tag in FAM_EVENTS and partnership_id is not None:
                dv = fe.text("DATE")
                ev = Event(
                    tree_id=tree.id,
                    relationship_id=partnership_id,
                    event_type=FAM_EVENTS[fe.tag],
                    date_value=dv,
                    date_start=_date_start(dv),
                    place_id=await place_id(fe.text("PLAC")),
                )
                session.add(ev)
                await session.flush()
                counts["events"] += 1

        for chil in rec.all("CHIL"):
            cp = person_map.get(chil.value.strip())
            if cp is None:
                continue
            for parent in (husb, wife):
                if parent and parent != cp:
                    session.add(
                        Relationship(
                            tree_id=tree.id,
                            type=RelationshipType.parent_child,
                            person_from_id=parent,
                            person_to_id=cp,
                            qualifier=ParentChildQualifier.biological,
                        )
                    )
                    counts["relationships"] += 1

    record_audit(
        session,
        action="import",
        entity_type="Gedcom",
        tree_id=tree.id,
        actor_user_id=actor.id,
        after=dict(counts),
    )
    await session.commit()
    return {"counts": dict(counts), "unmapped_tags": sorted(unmapped)}


def _ged_date(value: str | None) -> str | None:
    return value.strip() if value else None


async def export_gedcom(session: AsyncSession, *, viewer_id: uuid.UUID, tree: Tree) -> str:
    if not await privacy.can_view_tree(session, user_id=viewer_id, tree=tree):
        raise Forbidden("not permitted to view this tree")

    persons = list(
        (
            await session.execute(
                select(Person).where(Person.tree_id == tree.id, Person.deleted_at.is_(None))
            )
        ).scalars().all()
    )
    names = list(
        (
            await session.execute(
                select(Name).where(Name.tree_id == tree.id, Name.deleted_at.is_(None))
            )
        ).scalars().all()
    )
    events = list(
        (
            await session.execute(
                select(Event).where(Event.tree_id == tree.id, Event.deleted_at.is_(None))
            )
        ).scalars().all()
    )
    rels = list(
        (
            await session.execute(
                select(Relationship).where(
                    Relationship.tree_id == tree.id, Relationship.deleted_at.is_(None)
                )
            )
        ).scalars().all()
    )
    sources = list(
        (
            await session.execute(
                select(Source).where(Source.tree_id == tree.id, Source.deleted_at.is_(None))
            )
        ).scalars().all()
    )
    places = {
        p.id: p
        for p in (
            await session.execute(select(Place).where(Place.tree_id == tree.id))
        ).scalars().all()
    }

    pxref = {p.id: f"@I{i + 1}@" for i, p in enumerate(persons)}
    gender_by_id = {p.id: p.gender for p in persons}
    sxref = {s.id: f"@S{i + 1}@" for i, s in enumerate(sources)}
    names_by_person: dict[uuid.UUID, list[Name]] = defaultdict(list)
    for n in sorted(names, key=lambda n: (n.sort_order, not n.is_primary)):
        names_by_person[n.person_id].append(n)
    events_by_person: dict[uuid.UUID, list[Event]] = defaultdict(list)
    events_by_rel: dict[uuid.UUID, list[Event]] = defaultdict(list)
    for e in events:
        if e.person_id:
            events_by_person[e.person_id].append(e)
        elif e.relationship_id:
            events_by_rel[e.relationship_id].append(e)

    # Build families from parent-child + partnership edges (group by parent set).
    parents_of: dict[uuid.UUID, set[uuid.UUID]] = defaultdict(set)
    for r in rels:
        if r.type == RelationshipType.parent_child:
            parents_of[r.person_to_id].add(r.person_from_id)
    fams: dict[frozenset, dict] = {}
    for child, ps in parents_of.items():
        key = frozenset(ps)
        fams.setdefault(key, {"parents": set(ps), "children": [], "rel_id": None})
        fams[key]["children"].append(child)
    for r in rels:
        if r.type == RelationshipType.partnership:
            key = frozenset({r.person_from_id, r.person_to_id})
            fam = fams.setdefault(
                key,
                {"parents": {r.person_from_id, r.person_to_id}, "children": [], "rel_id": None},
            )
            fam["rel_id"] = r.id
    fam_list = list(fams.values())
    fxref = {id(f): f"@F{i + 1}@" for i, f in enumerate(fam_list)}
    # person -> the families they are a spouse in / a child in
    spouse_fams: dict[uuid.UUID, list[str]] = defaultdict(list)
    child_fams: dict[uuid.UUID, str] = {}
    for f in fam_list:
        x = fxref[id(f)]
        for pid in f["parents"]:
            spouse_fams[pid].append(x)
        for cid in f["children"]:
            child_fams[cid] = x

    out: list[str] = ["0 HEAD", "1 SOUR Provenance", "1 GEDC", "2 VERS 5.5.1", "1 CHAR UTF-8"]

    for p in persons:
        out.append(f"0 {pxref[p.id]} INDI")
        for n in names_by_person.get(p.id, []):
            display = n.display_name or f"{n.given or ''} /{n.surname or ''}/".strip()
            out.append(f"1 NAME {display}")
        sex = {"male": "M", "female": "F"}.get(p.gender or "")
        if sex:
            out.append(f"1 SEX {sex}")
        for e in events_by_person.get(p.id, []):
            tag = EVENT_TO_GED.get(e.event_type)
            if not tag:
                continue
            out.append(f"1 {tag}")
            if _ged_date(e.date_value):
                out.append(f"2 DATE {e.date_value}")
            if e.place_id and e.place_id in places:
                out.append(f"2 PLAC {places[e.place_id].name}")
        if p.id in child_fams:
            out.append(f"1 FAMC {child_fams[p.id]}")
        for x in spouse_fams.get(p.id, []):
            out.append(f"1 FAMS {x}")

    for f in fam_list:
        x = fxref[id(f)]
        out.append(f"0 {x} FAM")
        ps = list(f["parents"])
        # HUSB/WIFE by recorded gender where possible.
        males = [pid for pid in ps if gender_by_id.get(pid) == "male"]
        females = [pid for pid in ps if gender_by_id.get(pid) == "female"]
        husb = males[0] if males else (ps[0] if ps else None)
        wife = females[0] if females else next((pid for pid in ps if pid != husb), None)
        if husb:
            out.append(f"1 HUSB {pxref[husb]}")
        if wife:
            out.append(f"1 WIFE {pxref[wife]}")
        for cid in f["children"]:
            out.append(f"1 CHIL {pxref[cid]}")
        if f["rel_id"]:
            for e in events_by_rel.get(f["rel_id"], []):
                tag = EVENT_TO_GED.get(e.event_type)
                if not tag:
                    continue
                out.append(f"1 {tag}")
                if _ged_date(e.date_value):
                    out.append(f"2 DATE {e.date_value}")

    for s in sources:
        out.append(f"0 {sxref[s.id]} SOUR")
        if s.title:
            out.append(f"1 TITL {s.title}")
        if s.author:
            out.append(f"1 AUTH {s.author}")
        if s.publication_info:
            out.append(f"1 PUBL {s.publication_info}")

    out.append("0 TRLR")
    return "\n".join(out) + "\n"