import re
import io
from datetime import datetime
from typing import Optional, List, Any

import pdfplumber
from fastapi import FastAPI, UploadFile, File, HTTPException
from pydantic import BaseModel, Field


# ─────────────────────────────────────────────────────────────────────────────
# Pydantic models
# ─────────────────────────────────────────────────────────────────────────────

class VoucherLine(BaseModel):
    type: str = Field(
        default="E3k.Web.Objects.DataTransfer.VoucherLines.ArticleVoucherLine, E3k.Web.Objects.DataTransfer",
        alias="$type",
    )
    Number: str
    Quantity: float
    Price: float
    # SellPrice: float
    # Description: str = ""
    VatCode: str = "01"
    # DeliveryDate: Optional[str] = None

    model_config = {"populate_by_name": True}


class VoucherResponse(BaseModel):
    # Supplier: str
    OrderNumber: str
    DeliveryDate: Optional[str]
    CustomerNumber: Optional[str]
    VoucherDate: Optional[str]
    # Currency: str
    AdditionalFields: List[Any] = []
    VoucherLines: List[VoucherLine]


# ─────────────────────────────────────────────────────────────────────────────
# Sell-price markup
# ─────────────────────────────────────────────────────────────────────────────
SELL_PRICE_MARKUP = {
    "Trelleborg": 1.35,
    "Cleanfix":   1.30,
    "Polyflex":   1.30,
}


def sell_price(unit_price: float, supplier: str) -> float:
    markup = SELL_PRICE_MARKUP.get(supplier, 1.40)
    return round(unit_price * markup, 2)


# ─────────────────────────────────────────────────────────────────────────────
# Helpers
# ─────────────────────────────────────────────────────────────────────────────

def extract_text(pdf_bytes: bytes) -> str:
    parts = []
    with pdfplumber.open(io.BytesIO(pdf_bytes)) as pdf:
        for page in pdf.pages:
            t = page.extract_text()
            if t:
                parts.append(t)
    return "\n".join(parts)


def to_iso(raw: str) -> Optional[str]:
    raw = raw.strip()
    for fmt in ("%d.%m.%Y", "%d.%m.%y", "%d/%m/%Y", "%d/%m/%y"):
        try:
            return datetime.strptime(raw, fmt).date().isoformat()
        except ValueError:
            pass
    return raw


GERMAN_MONTHS = {
    "januar": "01", "februar": "02", "märz": "03", "april": "04",
    "mai": "05", "juni": "06", "juli": "07", "august": "08",
    "september": "09", "oktober": "10", "november": "11", "dezember": "12",
}


def german_date_to_iso(raw: str) -> Optional[str]:
    m = re.match(r"(\d{1,2})\.\s*(\w+)\s+(\d{4})", raw.strip(), re.IGNORECASE)
    if m:
        day = m.group(1).zfill(2)
        mon = GERMAN_MONTHS.get(m.group(2).lower())
        year = m.group(3)
        if mon:
            return f"{year}-{mon}-{day}"
    return to_iso(raw)


def num(s: str) -> float:
    return float(s.replace(",", "."))


# ─────────────────────────────────────────────────────────────────────────────
# Supplier identification
# ─────────────────────────────────────────────────────────────────────────────

def identify_supplier(text: str) -> str:
    upper = text.upper()
    if "TRELLEBORG" in upper:
        return "Trelleborg"
    if "CLEANFIX" in upper or re.search(r"Auftragsbestätigung VA\d+", text):
        return "Cleanfix"
    if "POLYFLEX" in upper:
        return "Polyflex"
    return "Unknown"


# ─────────────────────────────────────────────────────────────────────────────
# Parser: Trelleborg
# ─────────────────────────────────────────────────────────────────────────────
# Relevant extracted text structure:
#   IHRE REFERENZ VON RECHNUNG AN Referenzen
#   2600364 100 D01 Herr Baumann
#   UNSERE REFERENZ IE SCHLAUCHSERVICE BAUMANN GMBH
#   0010223953
#   ...
#   ADE - Alexandra DENEU +33 473 258 206 10/03/26 1/ 2
#   ...
#   Pos10 ZollNr : 4009410000 Ursp.:FR
#   0060068 CITERDIAL 38 L 13,30 11/03/26 M 13,3 52,51
#   %RAB: 33,00 35,181 467,91

def parse_trelleborg(text: str) -> VoucherResponse:
    lines = text.splitlines()

    # Voucher date from header line "10/03/26"
    voucher_date = None
    m = re.search(r"\b(\d{2}/\d{2}/\d{2})\b", text)
    if m:
        voucher_date = to_iso(m.group(1))

    # Our order number: first 7-digit number after "IHRE REFERENZ" line
    our_order = ""
    m = re.search(r"IHRE REFERENZ\b.*?\n(\d{7})\b", text, re.DOTALL)
    if m:
        our_order = m.group(1)

    # Supplier's reference number (UNSERE REFERENZ line, then next line)
    customer_num = None
    m = re.search(r"UNSERE REFERENZ\b.*?\n(\S+)", text, re.DOTALL)
    if m:
        customer_num = m.group(1)

    # Article lines — 3-line block per article:
    #   Line A: Pos10 ZollNr : 4009410000 Ursp.:FR
    #   Line B: 0060068 CITERDIAL 38 L 13,30 11/03/26 M 13,3 52,51
    #   Line C: %RAB: 33,00 35,181 467,91
    block_re = re.compile(
        r"Pos\d+\s+ZollNr\s*:\s*\S+\s+Ursp\.:\s*\S+\s*\n"
        r"(\S+)\s+(.+?)\s+(\d{2}/\d{2}/\d{2})\s+M\s+([\d,]+)\s+([\d,]+)\s*\n"
        r"\s*%RAB:\s*([\d,]+)\s+([\d,]+)\s+([\d,]+)",
        re.DOTALL,
    )

    voucher_lines = []
    delivery_date = voucher_date

    for m in block_re.finditer(text):
        art_num    = m.group(1)
        desc       = m.group(2).strip()
        line_date  = to_iso(m.group(3))
        qty        = num(m.group(4))
        unit_price = num(m.group(5))   # gross unit price
        # group(6) = %RAB (discount %)
        net_price  = num(m.group(7))   # unit price after discount

        if delivery_date == voucher_date and line_date:
            delivery_date = line_date

        voucher_lines.append(VoucherLine(**{
            "$type": "E3k.Web.Objects.DataTransfer.VoucherLines.ArticleVoucherLine, E3k.Web.Objects.DataTransfer",
            "Number":       art_num,
            "Quantity":     qty,
            "Price":        round(net_price, 4),
            # "SellPrice":    sell_price(net_price, "Trelleborg"),
            # "Description":  desc,
            "VatCode":      "01",
            # "DeliveryDate": line_date,
        }))

    return VoucherResponse(
        # Supplier="Trelleborg",
        OrderNumber=our_order,
        DeliveryDate=delivery_date,
        CustomerNumber=customer_num,
        VoucherDate=voucher_date,
        # Currency="EUR",
        VoucherLines=voucher_lines,
    )


# ─────────────────────────────────────────────────────────────────────────────
# Parser: Cleanfix
# ─────────────────────────────────────────────────────────────────────────────
# Relevant extracted text structure:
#   Datum 10.03.2026
#   Ihre Bestellnr. 2600370
#   Debitorennr. 35228
#   Auslieferdatum 11.03.2026
#   Auftragsbestätigung VA516165
#   Pos Artikelnr. Menge / Einheit VK-Preis % Betrag
#   1 710.657 2.00Stück 87.05 35 113.16      ← no space between qty and "Stück"!
#   Ladesteckdose FT80A 16mm2
#   2 710.656 2.00Stück 64.40 35 83.72
#   Ladestecker FT80A 16mm2
#   3 607.000 1.00Stück 105.75 35 68.74
#   Treppenadapter 1Düse, 23cm

def parse_cleanfix(text: str) -> VoucherResponse:
    # Voucher date
    voucher_date = None
    m = re.search(r"Datum\s+(\d{2}\.\d{2}\.\d{4})", text)
    if m:
        voucher_date = to_iso(m.group(1))

    # Delivery date
    delivery_date = voucher_date
    m = re.search(r"Auslieferdatum\s+(\d{2}\.\d{2}\.\d{4})", text)
    if m:
        delivery_date = to_iso(m.group(1))

    # Our order number
    our_order = ""
    m = re.search(r"Ihre Bestellnr\.\s+(\d+)", text)
    if m:
        our_order = m.group(1)

    # Customer number
    customer_num = None
    m = re.search(r"Debitorennr\.\s+(\S+)", text)
    if m:
        customer_num = m.group(1)

    # Article line pattern:
    # "1 710.657 2.00Stück 87.05 35 113.16"
    # qty and "Stück" are concatenated ("2.00Stück") in the extracted text
    line_re = re.compile(
        r"^(\d+)\s+([\d.]+)\s+([\d.]+)Stück\s+([\d.]+)\s+([\d.]+)\s+([\d.]+)\s*$",
        re.MULTILINE,
    )

    all_lines = text.splitlines()
    voucher_lines = []

    for m in line_re.finditer(text):
        art_num    = m.group(2)
        qty        = float(m.group(3))
        unit_price = float(m.group(4))   # VK-Preis (gross)
        discount   = float(m.group(5))   # discount %
        # line total = m.group(6)

        # Description is on the very next line
        match_end_line = text[:m.end()].count("\n")
        desc = ""
        if match_end_line + 1 < len(all_lines):
            candidate = all_lines[match_end_line + 1].strip()
            # Skip if it's another article row, a total line, or a thank-you line
            if candidate and not re.match(r"^\d+\s+[\d.]+\s+[\d.]+Stück", candidate) \
                         and not candidate.startswith("Total") \
                         and not candidate.startswith("Besten"):
                desc = candidate

        voucher_lines.append(VoucherLine(**{
            "$type": "E3k.Web.Objects.DataTransfer.VoucherLines.ArticleVoucherLine, E3k.Web.Objects.DataTransfer",
            "Number":       art_num,
            "Quantity":     qty,
            "Price":        unit_price,
            # "SellPrice":    sell_price(unit_price, "Cleanfix"),
            # "Description":  desc,
            "VatCode":      "01",
            # "DeliveryDate": delivery_date,
        }))

    return VoucherResponse(
        # Supplier="Cleanfix",
        OrderNumber=our_order,
        DeliveryDate=delivery_date,
        CustomerNumber=customer_num,
        VoucherDate=voucher_date,
        # Currency="CHF",
        VoucherLines=voucher_lines,
    )


# ─────────────────────────────────────────────────────────────────────────────
# Parser: Polyflex
# ─────────────────────────────────────────────────────────────────────────────
# Relevant extracted text structure:
#   Kundennummer: D00030
#   Ihre Bestellung 2600357
#   Würenlos, 06.03.26
#   21200025 Schlauch POLYWELL antistatisch 60.00 Meter 6.80 45.00 224.40
#   id=25mm, 2x30m
#   Warenausgangsdatum: 6. März 2026

def parse_polyflex(text: str) -> VoucherResponse:
    # Voucher date  "Würenlos, 06.03.26"
    voucher_date = None
    m = re.search(r"Würenlos,?\s+(\d{2}\.\d{2}\.\d{2,4})", text)
    if m:
        voucher_date = to_iso(m.group(1))

    # Dispatch / delivery date  "Warenausgangsdatum: 6. März 2026"
    delivery_date = voucher_date
    m = re.search(r"Warenausgangsdatum:\s+(.+)", text)
    if m:
        delivery_date = german_date_to_iso(m.group(1).strip())

    # Our order number
    our_order = ""
    m = re.search(r"Ihre Bestellung\s+(\d+)", text)
    if m:
        our_order = m.group(1)

    # Customer number
    customer_num = None
    m = re.search(r"Kundennummer:\s+(\S+)", text)
    if m:
        customer_num = m.group(1)

    # Article line:
    # "21200025 Schlauch POLYWELL antistatisch 60.00 Meter 6.80 45.00 224.40"
    line_re = re.compile(
        r"^(\d{5,12})\s+(.+?)\s+([\d.]+)\s+Meter\s+([\d.]+)\s+([\d.]+)\s+([\d.]+)\s*$",
        re.MULTILINE,
    )

    all_lines = text.splitlines()
    voucher_lines = []

    for m in line_re.finditer(text):
        art_num    = m.group(1)
        desc       = m.group(2).strip()
        qty        = float(m.group(3))
        unit_price = float(m.group(4))
        # discount  = float(m.group(5))
        # total     = float(m.group(6))

        # Append continuation description line (e.g. "id=25mm, 2x30m")
        match_end_line = text[:m.end()].count("\n")
        if match_end_line + 1 < len(all_lines):
            nxt = all_lines[match_end_line + 1].strip()
            if nxt and not re.match(r"^\d{5,}", nxt) and not nxt.startswith("Total"):
                desc += " " + nxt

        voucher_lines.append(VoucherLine(**{
            "$type": "E3k.Web.Objects.DataTransfer.VoucherLines.ArticleVoucherLine, E3k.Web.Objects.DataTransfer",
            "Number":       art_num,
            "Quantity":     qty,
            "Price":        unit_price,
            # "SellPrice":    sell_price(unit_price, "Polyflex"),
            # "Description":  desc,
            "VatCode":      "01",
            # "DeliveryDate": delivery_date,
        }))

    return VoucherResponse(
        # Supplier="Polyflex",
        OrderNumber=our_order,
        DeliveryDate=delivery_date,
        CustomerNumber=customer_num,
        VoucherDate=voucher_date,
        # Currency="CHF",
        VoucherLines=voucher_lines,
    )


# ─────────────────────────────────────────────────────────────────────────────
# Dispatcher
# ─────────────────────────────────────────────────────────────────────────────

def parse_pdf(pdf_bytes: bytes) -> VoucherResponse:
    text = extract_text(pdf_bytes)
    supplier = identify_supplier(text)

    if supplier == "Trelleborg":
        return parse_trelleborg(text)
    if supplier == "Cleanfix":
        return parse_cleanfix(text)
    if supplier == "Polyflex":
        return parse_polyflex(text)

    raise ValueError(
        f"Could not identify supplier.\nExtracted text snippet:\n{text[:400]}"
    )


# ─────────────────────────────────────────────────────────────────────────────
# FastAPI
# ─────────────────────────────────────────────────────────────────────────────

app = FastAPI(
    title="Order Confirmation PDF Extractor",
    description=(
        "Upload a supplier order-confirmation PDF "
        "(Trelleborg / Cleanfix / Polyflex) and receive ERP-ready JSON."
    ),
    version="2.0.0",
)


@app.post(
    "/extract",
    response_model=VoucherResponse,
    summary="Extract order data from a supplier PDF",
)
async def extract_order(
    file: UploadFile = File(..., description="Supplier order-confirmation PDF"),
):
    if not file.filename.lower().endswith(".pdf"):
        raise HTTPException(status_code=400, detail="Only PDF files are accepted.")

    content = await file.read()
    try:
        result = parse_pdf(content)
    except ValueError as e:
        raise HTTPException(status_code=422, detail=str(e))
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"Parsing error: {e}")

    return result


@app.get("/health", summary="Health check")
def health():
    return {"status": "ok"}