vis.py

import requests
import json
import typing as t
import datetime

URL_VNV = (
    "http://px.hagstofa.is/pxis/api/v1/is/Efnahagur/visitolur/1_vnv/1_vnv/VIS01000.px"
)
URL_VH = "https://talnaefni.fasteignaskra.is/talnaefni/v1/ibudavisitala"
BODY_VNV = {
    "query": [
        {"code": "Vísitala", "selection": {"filter": "item", "values": ["CPI"]}},
        {"code": "Liður", "selection": {"filter": "item", "values": ["index"]}},
    ],
    "response": {"format": "json"},
}


def visitala_neysluverds() -> t.Dict[str, float]:
    """Gets latest consumer price index for Statistics of Iceland"""

    r = requests.post(URL_VNV, json=BODY_VNV)
    json_response = json.loads(r.content)

    vnv: t.Dict[str, float] = dict()
    for row in json_response["data"]:
        month = row["key"][0].replace("M", "-")
        vnv[month] = float(row["values"][0])

    return vnv


def visitala_ibudaverds() -> t.Dict[str, float]:
    """Gets latest property price index for all properties in the capital region."""

    r = requests.get(URL_VH)
    json_response = json.loads(r.content)

    vh: t.Dict[str, float] = dict()
    for row in json_response:
        month = f"{row['Ar']}-{str(row['Manudur']).rjust(2, '0')}"
        vh[month] = float(row["Vst_heild"])

    return vh


def months_between(d1: datetime.date, d2: datetime.date) -> int:
    return (d1.year - d2.year) * 12 + d1.month - d2.month


def check_data(data: t.Dict[str, float], origin: datetime.date) -> None:
    """Checks if the data is within expected length raises Exception if errors are found."""

    latest_date = datetime.datetime.strptime(
        f"{list(data.keys())[-1]}-01", "%Y-%m-%d"
    ).date()

    if datetime.date.today() - datetime.timedelta(days=90) > latest_date:
        raise ValueError("Latest date is not within boundaries")

    if len(data) != months_between(latest_date, origin) + 1:
        raise ValueError("Missing dates in the dataset")


def main() -> int:
    """Constructs vis.js accoring to the original format of the file"""

    vnv = visitala_neysluverds()
    vh = visitala_ibudaverds()

    # Simple data checks to make sure not to break
    # the website if data is missing.
    check_data(vnv, datetime.date(1988, 5, 1))
    check_data(vh, datetime.date(1994, 1, 1))

    with open("vis.js", "w", encoding="utf-8") as f:

        f.writelines("// Vísitölur húsnæðisverðs og neysluverðs\n")
        f.writelines(
            "// Sjá https://fasteignaskra.is/gogn/fasteignagattin/fasteignavidskipti/visitolur-ibuda-og-leiguverds/\n"
        )
        f.writelines(
            "// og https://hagstofa.is/talnaefni/efnahagur/verdlag/visitala-neysluverds/\n\n"
        )

        f.writelines("var vis = {\n")
        for key, vnv_value in vnv.items():

            vh_value = vh.get(key)

            # Ignore latest records if both vnv and vh do not exist
            # Before 1994, there are only records available for vnv
            if int(key[:4]) >= 1994 and not vh_value:
                continue

            f.writelines(f'"{key}" : {{ vnv: {vnv_value}')
            if vh_value:
                f.writelines(f", vh: {vh_value}")
            f.writelines(" },\n")

        f.writelines("};")

    return 0


if __name__ == "__main__":
    exit(main())