115 lines
4.1 KiB
Python
115 lines
4.1 KiB
Python
#!/usr/bin/env python3
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"""Rebuild data/misc/timezone.tsv from the IANA tzdb tarball (public domain).
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data-import/timezone.py [--source URL_OR_FILE] [--cache DIR] [--out FILE] [--territories FILE]
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The offset is the zone's standard offset, the first field of its Zone rule's last
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continuation line, with a Link resolved to its target.
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"""
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import argparse
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import csv
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import io
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import re
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import sys
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import tarfile
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from pathlib import Path
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import source
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import tsv
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SOURCE = "https://data.iana.org/time-zones/tzdata-latest.tar.gz"
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OUT = Path(__file__).resolve().parent.parent / "data" / "misc" / "timezone.tsv"
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TERRITORIES = Path(__file__).resolve().parent.parent / "data" / "misc" / "territory.tsv"
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CACHE = Path(__file__).resolve().parent / "cache"
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COLUMNS = ["offset", "territory", "zone"]
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REGIONS = ["africa", "antarctica", "asia", "australasia", "backward", "etcetera", "europe", "northamerica", "southamerica"]
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def member(tar, name):
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try:
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return tar.extractfile(name).read().decode("utf-8")
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except KeyError:
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sys.exit(f"{name}: the tarball no longer holds it; the tzdb layout has moved")
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def offsets(tar):
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"""Every zone's standard offset, and every link's target."""
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std, links = {}, {}
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for name in REGIONS:
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zone = None
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for raw in member(tar, name).splitlines():
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line = raw.split("#")[0].rstrip()
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if not line.strip():
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continue
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if line.startswith("Zone"):
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f = line.split()
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zone, std[f[1]] = f[1], f[2]
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elif line.startswith("Link"):
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f = line.split()
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links[f[2]], zone = f[1], None
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elif line[0] in " \t" and zone:
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std[zone] = line.split()[0]
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else:
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zone = None
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return std, links
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def resolve(zone, std, links):
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for _ in range(10):
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if zone in std:
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return std[zone]
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if zone not in links:
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return None
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zone = links[zone]
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return None
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def utc_offset(raw):
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"""±HH:MM from a tzdb STDOFF field, which writes the minutes and seconds only when it has them."""
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m = re.match(r"^(-)?(\d{1,2})(?::(\d{2})(?::(\d{2}))?)?$", raw)
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if not m or (m.group(4) or "00") != "00":
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return None
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return f"{'-' if m.group(1) else '+'}{int(m.group(2)):02d}:{m.group(3) or '00'}"
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def rows(tar, territories):
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std, links = offsets(tar)
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for line in member(tar, "zone.tab").splitlines():
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if line.startswith("#") or not line.strip():
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continue
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fields = line.split("\t")
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if len(fields) < 3:
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sys.exit(f"zone.tab: {line!r} has {len(fields)} fields; a row names a territory, a location and a zone")
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territory, zone = fields[0], fields[2]
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if territory not in territories:
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continue
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raw = resolve(zone, std, links)
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if raw is None:
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sys.exit(f"{zone}: the tarball gives it no Zone rule and no Link to one")
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offset = utc_offset(raw)
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if offset is None:
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sys.exit(f"{zone}: standard offset {raw!r} is not a ±HH:MM the table can spell")
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yield {"offset": offset, "territory": territory, "zone": zone}
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def main():
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p = argparse.ArgumentParser(description=__doc__.splitlines()[0])
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p.add_argument("--cache", default=str(CACHE))
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p.add_argument("--source", default=SOURCE)
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p.add_argument("--out", default=str(OUT))
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p.add_argument("--territories", default=str(TERRITORIES))
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a = p.parse_args()
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shipped = {r["alpha2"] for r in csv.DictReader(io.StringIO(Path(a.territories).read_text(encoding="utf-8")), delimiter="\t")}
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body = source.fetch(a.source, a.cache, "tzdata-latest.tar.gz", magic=b"\x1f\x8b")
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with tarfile.open(fileobj=io.BytesIO(body)) as tar:
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table = sorted(rows(tar, shipped), key=lambda r: r["zone"])
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print(f"tzdb {tar.extractfile('version').read().decode('utf-8').strip()}", file=sys.stderr)
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linked = {r["territory"] for r in table}
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if missing := shipped - linked:
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sys.exit(f"no zone for {sorted(missing)}; a parent row without a child is a load error")
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tsv.write(a.out, COLUMNS, table)
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if __name__ == "__main__":
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main()
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