"""Pure parsing helpers for single cell values. No workbook access here."""

from __future__ import annotations

import re
from dataclasses import dataclass, field

# Canonical unit keys (shared with the app) and the spellings found in the workbook.
UNIT_ALIASES: dict[str, list[str]] = {
    "gram": ["gramm", "g", "gr"],
    "kilogram": ["kilogramm", "kg"],
    "milliliter": ["milliliter", "mililiter", "ml"],
    "liter": ["liter", "l"],
    "tablespoon": ["esslöffel", "el"],
    "teaspoon": ["teelöffel", "tl"],
    "pinch": ["prise", "prisen"],
    "knifeTip": ["msp.", "msp", "messerspitze"],
    "pack": ["packung", "pkt.", "pkt", "päckchen"],
    "can": ["dose"],
    "jar": ["glas"],
    "tub": ["becher"],
    "bag": ["beutel"],
    "carton": ["karton"],
    "bunch": ["bund"],
    "head": ["kopf"],
    "slice": ["scheibe/n", "scheibe", "scheiben"],
    "clove": ["zehe/n", "zehe", "zehen"],
    "sprig": ["zweig (e)", "zweig", "zweige"],
    "handful": ["handvoll", "hand voll"],
    "cup": ["tasse", "tassen"],
    "grain": ["körner", "korn"],
    "piece": ["stück", "stk.", "stk"],
    "small": ["kleine", "klein", "kleiner", "kleines"],
    "medium": ["mittel", "mittlere", "mittelgroße"],
    "large": ["große", "groß", "großer", "großes"],
    "some": ["etwas"],
}
_UNIT_LOOKUP = {alias: key for key, aliases in UNIT_ALIASES.items() for alias in aliases}

_FRACTIONS = {"½": 0.5, "¼": 0.25, "¾": 0.75, "⅓": 1 / 3, "⅔": 2 / 3, "⅛": 0.125}
_NUMBER = r"\d+(?:[.,]\d+)?"


def clean(value) -> str | None:
    """Cell value as stripped text, or None when empty."""
    if value is None:
        return None
    text = str(value).replace("\r\n", "\n").strip()
    return text or None


def _round(x: float) -> float | int:
    x = round(x, 3)
    return int(x) if x == int(x) else x


def _single_amount(text: str) -> float | None:
    text = text.strip()
    if text in _FRACTIONS:
        return _FRACTIONS[text]
    m = re.fullmatch(rf"(\d+)\s*([½¼¾⅓⅔⅛])", text)
    if m:
        return int(m.group(1)) + _FRACTIONS[m.group(2)]
    m = re.fullmatch(r"(?:(\d+)\s+)?(\d+)\s*/\s*(\d+)", text)
    if m and int(m.group(3)) != 0:
        return int(m.group(1) or 0) + int(m.group(2)) / int(m.group(3))
    if re.fullmatch(_NUMBER, text):
        return float(text.replace(",", "."))
    return None


def parse_amount(value) -> tuple[float | int | None, float | int | None] | None:
    """(amount, amountMax) from a quantity cell; None when the text is not a quantity."""
    if value is None:
        return (None, None)
    if isinstance(value, (int, float)):
        return (_round(float(value)), None) if value != 0 else (None, None)
    text = clean(value)
    if text is None:
        return (None, None)
    parts = re.split(r"\s*(?:-|–|bis)\s*", text)
    if len(parts) == 2:
        low, high = _single_amount(parts[0]), _single_amount(parts[1])
        if low is not None and high is not None:
            return (_round(low), _round(high))
    single = _single_amount(text)
    if single is not None:
        return (_round(single), None) if single != 0 else (None, None)
    return None


def parse_unit(value) -> str | None:
    """Canonical unit key for a unit cell, or None when unrecognised."""
    text = clean(value)
    if text is None:
        return None
    return _UNIT_LOOKUP.get(text.lower())


def split_amount_unit(value) -> tuple[float | int, str | None] | None:
    """'100 g' / '1 TL' / '3' typed into the unit column -> (amount, unit key)."""
    text = clean(value)
    if text is None:
        return None
    m = re.fullmatch(rf"({_NUMBER})\s*(.*)", text)
    if not m:
        return None
    amount = _round(float(m.group(1).replace(",", ".")))
    rest = m.group(2).strip()
    if not rest:
        return (amount, None)
    unit = parse_unit(rest)
    return (amount, unit) if unit else None


def is_number(value) -> bool:
    if isinstance(value, (int, float)):
        return True
    text = clean(value)
    return text is not None and re.fullmatch(_NUMBER, text) is not None


def parse_minutes(value) -> int | None | str:
    """Minutes from a time cell. Returns the original text when it cannot be read."""
    if value is None:
        return None
    if isinstance(value, (int, float)):
        return int(round(value)) or None
    text = clean(value)
    if text is None:
        return None
    total, matched = 0.0, False
    for num, unit in re.findall(rf"({_NUMBER})\s*(stunden|stunde|std\.?|h|minuten|min\.?|m)?\b", text.lower()):
        n = float(num.replace(",", "."))
        total += n * 60 if unit and unit[0] in "sh" else n
        matched = True
    if not matched:
        return text
    return int(round(total)) or None


@dataclass
class Servings:
    value: float | int | None
    remark: str | None = None  # leftover text such as "8 Stk." that does not fit the number


def parse_servings(value) -> Servings:
    if value is None:
        return Servings(None)
    if isinstance(value, (int, float)):
        return Servings(_round(float(value)) or None)
    text = clean(value)
    if text is None:
        return Servings(None)
    m = re.match(rf"({_NUMBER})\s*(.*)", text, re.S)
    if not m:
        return Servings(None, text)
    number = _round(float(m.group(1).replace(",", ".")))
    rest = m.group(2).strip()
    if rest.lower() in ("", "portion", "portionen", "person", "personen"):
        return Servings(number)
    return Servings(number, text)


WHOLE_RECIPE_THRESHOLD = 1500


def calories_basis(kcal: float) -> str:
    """Guessed basis for a bare kcal value (agreed rule: above 1500 means the whole recipe)."""
    return "wholeRecipe" if kcal > WHOLE_RECIPE_THRESHOLD else "perServing"


_URL = re.compile(r"https?://\S+")


def extract_urls(text: str) -> tuple[list[str], str | None]:
    """URLs found in text, and the text that remains without them."""
    urls = _URL.findall(text)
    rest = _URL.sub("", text).strip()
    return urls, (rest or None)


# --- Steps -------------------------------------------------------------------

LONG_STEP_CHARS = 600

_INLINE_HEADING = re.compile(r"^([A-ZÄÖÜ][\wäöüß\-]*(?: [\wäöüß\-]+){0,2}):\s*(\S.*)$", re.S)
_ENUMERATION = re.compile(r"^(?:schritt\s*)?\d+\s*[.):]\s+", re.I)


def _is_heading(line: str) -> bool:
    return len(line) <= 40 and not re.search(r"[.!?]$", line) and len(line.split()) <= 4


@dataclass
class StepSection:
    title: str | None
    steps: list[str] = field(default_factory=list)


def split_steps(text: str | None) -> list[StepSection]:
    """Instruction text -> Step Sections. Blank lines separate Steps; short lines become headings."""
    if not text:
        return []
    lines = [line.strip() for line in text.replace("\r\n", "\n").split("\n")]
    body = "\n".join(lines).strip()
    if not body:
        return []
    paragraphs = [p.strip() for p in re.split(r"\n{2,}", body) if p.strip()]
    if len(paragraphs) == 1 and "\n" in paragraphs[0]:
        paragraphs = [line for line in paragraphs[0].split("\n") if line]

    sections = [StepSection(None)]

    def add_step(step: str) -> None:
        step = _ENUMERATION.sub("", step).strip()
        if step:
            sections[-1].steps.append(step)

    for i, para in enumerate(paragraphs):
        head, *rest = para.split("\n")
        is_last = i == len(paragraphs) - 1
        if _is_heading(head) and (rest or not is_last):
            # "Teig\nMehl verkneten…" or a lone "Teig" line before the next paragraph.
            sections.append(StepSection(head.rstrip(":").strip()))
            if rest:
                add_step("\n".join(rest))
            continue
        m = _INLINE_HEADING.match(para)
        if m:
            # "Soße:Die vegane Mayonnaise…"
            sections.append(StepSection(m.group(1)))
            add_step(m.group(2))
            continue
        add_step(para)

    return [s for s in sections if s.steps]