from __future__ import annotations

import json
import re
from datetime import date as Date
from datetime import datetime as DateTime
from decimal import Decimal, ROUND_HALF_UP
from enum import StrEnum
from typing import Any

from pydantic import BaseModel, ConfigDict, Field, field_validator

from app.config import CATEGORIES, DOC_KINDS

_FENCE_RE = re.compile(r"```(?:json)?\s*(.*?)\s*```", re.DOTALL | re.IGNORECASE)


class ReceiptStatus(StrEnum):
    queued = "queued"
    processing = "processing"
    needs_ocr = "needs_ocr"
    needs_extract = "needs_extract"
    needs_review = "needs_review"
    confirmed = "confirmed"
    failed = "failed"
    duplicate = "duplicate"


class MatchBand(StrEnum):
    exact = "exact"
    auto = "auto"
    review = "review"
    unmatched = "unmatched"
    confirmed = "confirmed"


class LineItem(BaseModel):
    model_config = ConfigDict(extra="forbid")

    description: str
    qty: float | None = None
    unit_price: Decimal | None = None
    amount: Decimal | None = None
    sku: str | None = None


class ReceiptExtract(BaseModel):
    model_config = ConfigDict(extra="forbid")

    doc_kind: str = "receipt"
    category: str = "other"
    vendor: str | None = None
    date: Date | None = None
    tax: Decimal | None = None
    total: Decimal | None = None
    currency: str | None = None
    line_items: list[LineItem] = Field(default_factory=list)

    @field_validator("doc_kind")
    @classmethod
    def _doc_kind(cls, value: str) -> str:
        kind = (value or "receipt").strip().lower()
        return kind if kind in DOC_KINDS else "document"

    @field_validator("category")
    @classmethod
    def _category(cls, value: str) -> str:
        cat = (value or "other").strip().lower()
        return cat if cat in CATEGORIES else "other"

    @field_validator("date", mode="before")
    @classmethod
    def _date(cls, value: object) -> object:
        if value in (None, "", "null"):
            return None
        if isinstance(value, Date):
            return value
        text = str(value).strip()[:10]
        return DateTime.strptime(text, "%Y-%m-%d").date()


class MatchHit(BaseModel):
    catalog_id: int | None = None
    sku: str | None = None
    vendor: str | None = None
    description: str | None = None
    similarity: float
    band: MatchBand
    reason: str


class ProcessResult(BaseModel):
    receipt_id: int | None = None
    status: ReceiptStatus
    source_path: str
    extract: ReceiptExtract | None = None
    matches: list[MatchHit] = Field(default_factory=list)
    error: str | None = None


def to_cents(value: Decimal | float | int | None) -> int | None:
    if value is None:
        return None
    quantized = (Decimal(str(value)) * 100).quantize(Decimal("1"), rounding=ROUND_HALF_UP)
    return int(quantized)


def cents_to_decimal(cents: int | None) -> Decimal | None:
    if cents is None:
        return None
    return (Decimal(cents) / Decimal("100")).quantize(Decimal("0.01"))


def extract_json_object(text: str) -> str:
    stripped = text.strip()
    fenced = _FENCE_RE.search(stripped)
    if fenced:
        stripped = fenced.group(1).strip()
    start = stripped.find("{")
    end = stripped.rfind("}")
    if start < 0 or end <= start:
        raise ValueError("no JSON object in model output")
    return stripped[start : end + 1]


def parse_extract_json(text: str) -> ReceiptExtract:
    payload = json.loads(extract_json_object(text))
    if not isinstance(payload, dict):
        raise ValueError("extract JSON must be an object")
    if "line_items" not in payload or payload["line_items"] is None:
        payload["line_items"] = []
    return ReceiptExtract.model_validate(payload)


EXTRACT_JSON_SCHEMA: dict[str, Any] = ReceiptExtract.model_json_schema()