#!/usr/bin/env python3
"""
imp2ics: Convert OKsoftware "Svátky a výročí" (.imp) files to RFC 5545 iCalendar (.ics) and Google Calendar CSV.
Developed for Kof / Dell backup restoration.

Supports strict RFC 5545 compliance:
- CRLF line endings
- 75-octet line folding
- DTSTART and DTEND (DATE format, exclusive DTEND = next day)
- TRANSP:TRANSPARENT (all-day events don't block user availability)
- RRULE:FREQ=YEARLY for recurring dates
- Proper text escaping (commas, semicolons, backslashes, newlines)
- CSV export for Google Calendar and Microsoft Outlook
"""
import sys
import os
import io
import csv
import glob
import re
import struct
import uuid
from datetime import datetime, timedelta, timezone

DELPHI_EPOCH = datetime(1899, 12, 30)

TYPE_NAMES = {
    0: "Narozeniny",
    1: "Výročí",
    2: "Událost",
    3: "Připomenutí",
    4: "Svátek"
}

def normalize_name(name):
    s = re.sub(r'\s+', ' ', name.strip())
    s = re.sub(r'^\*\s*', '* ', s)
    s = re.sub(r'^\†\s*', '† ', s)
    return s

def escape_ics_text(text):
    if not text:
        return ""
    s = str(text)
    s = s.replace('\\', '\\\\')
    s = s.replace(';', r'\;')
    s = s.replace(',', r'\,')
    s = s.replace('\r\n', r'\n').replace('\r', r'\n').replace('\n', r'\n')
    return s

def fold_line(line, limit=75):
    encoded = line.encode('utf-8')
    if len(encoded) <= limit:
        return line
    parts = []
    while len(encoded) > limit:
        cut = limit
        # Walk backward if we land in the middle of a multi-byte UTF-8 character
        while cut > 0 and (encoded[cut] & 0xC0) == 0x80:
            cut -= 1
        parts.append(encoded[:cut].decode('utf-8'))
        encoded = b' ' + encoded[cut:]
    if encoded:
        parts.append(encoded.decode('utf-8'))
    return "\r\n".join(parts)

def parse_imp(filepath):
    with open(filepath, 'rb') as f:
        data = f.read()

    pos = 0
    tokens = []
    while pos < len(data):
        b = data[pos]
        pos += 1
        if b == 0x00:
            tokens.append(('END', None))
        elif b == 0x01:
            tokens.append(('LIST', None))
        elif b == 0x02:
            tokens.append(('INT8', data[pos]))
            pos += 1
        elif b == 0x03:
            tokens.append(('INT16', struct.unpack('<h', data[pos:pos+2])[0]))
            pos += 2
        elif b == 0x04:
            tokens.append(('INT32', struct.unpack('<i', data[pos:pos+4])[0]))
            pos += 4
        elif b == 0x06:
            slen = data[pos]
            pos += 1
            s = data[pos:pos+slen].decode('utf-8', errors='replace')
            pos += slen
            tokens.append(('STR', s))
        elif b == 0x14:
            slen = struct.unpack('<I', data[pos:pos+4])[0]
            pos += 4
            s = data[pos:pos+slen].decode('utf-8', errors='replace')
            pos += slen
            tokens.append(('STR', s))
        else:
            pass

    events = []
    i = 0
    while i < len(tokens):
        t = tokens[i]
        if t[0] in ('INT16', 'INT32'):
            days = t[1]
            if i + 2 < len(tokens) and tokens[i+1][0] == 'INT8' and tokens[i+2][0] == 'STR':
                etype = tokens[i+1][1]
                ename = tokens[i+2][1].strip()
                try:
                    dt = DELPHI_EPOCH + timedelta(days=days)
                    events.append({
                        "date": dt,
                        "type": etype,
                        "name": ename,
                        "source": os.path.basename(filepath)
                    })
                except OverflowError:
                    pass
                i += 3
                continue
        i += 1
    return events

def deduplicate_events(events):
    seen = {}
    for ev in events:
        nname = normalize_name(ev["name"])
        dt = ev["date"]
        etype = ev["type"]
        key = (nname.lower(), dt.month, dt.day, etype)
        if key not in seen:
            ev_copy = dict(ev)
            ev_copy["name"] = nname
            seen[key] = ev_copy
    return list(seen.values())

def events_to_ics(events, cal_name="Svátky a výročí"):
    deduped = deduplicate_events(events)
    now_str = datetime.now(timezone.utc).strftime("%Y%m%dT%H%M%SZ")

    raw_lines = [
        "BEGIN:VCALENDAR",
        "VERSION:2.0",
        "PRODID:-//Antigravity Fleet//Svátky a výročí 2006//CS",
        "CALSCALE:GREGORIAN",
        "METHOD:PUBLISH",
        f"X-WR-CALNAME:{escape_ics_text(cal_name)}",
        "X-WR-TIMEZONE:Europe/Prague"
    ]

    for ev in deduped:
        dt = ev["date"]
        dt_end = dt + timedelta(days=1)
        etype = ev["type"]
        ename = ev["name"]
        tname = TYPE_NAMES.get(etype, "Událost")

        uid = str(uuid.uuid5(uuid.NAMESPACE_DNS, f"{ename}_{dt.strftime('%Y%m%d')}_{etype}"))
        dt_str = dt.strftime("%Y%m%d")
        dt_end_str = dt_end.strftime("%Y%m%d")

        raw_lines.append("BEGIN:VEVENT")
        raw_lines.append(f"UID:{uid}")
        raw_lines.append(f"DTSTAMP:{now_str}")
        raw_lines.append(f"DTSTART;VALUE=DATE:{dt_str}")
        raw_lines.append(f"DTEND;VALUE=DATE:{dt_end_str}")
        raw_lines.append(f"SUMMARY:{escape_ics_text(ename)}")

        if etype == 0:
            desc = f"Narozeniny: {ename}\nRok narození: {dt.year}"
        elif etype == 1:
            desc = f"Výročí: {ename}\nOd roku: {dt.year}"
        elif etype == 4:
            desc = f"Svátek: {ename}"
        else:
            desc = f"{tname}: {ename}\nZáznam z roku: {dt.year}"

        raw_lines.append(f"DESCRIPTION:{escape_ics_text(desc)}")
        raw_lines.append(f"CATEGORIES:{escape_ics_text(tname)}")
        raw_lines.append("STATUS:CONFIRMED")
        raw_lines.append("TRANSP:TRANSPARENT")

        if etype != 3:  # Only one-off reminders do not recur
            raw_lines.append("RRULE:FREQ=YEARLY")

        raw_lines.append("END:VEVENT")

    raw_lines.append("END:VCALENDAR")

    folded_lines = [fold_line(line) for line in raw_lines]
    return "\r\n".join(folded_lines) + "\r\n"

def events_to_csv(events, project_upcoming_years=1):
    """
    Export events to Google Calendar / Outlook CSV format.
    If project_upcoming_years > 1, generates repeating occurrences for future years
    (since CSV does not natively support RRULE recurrence).
    """
    deduped = deduplicate_events(events)
    output = io.StringIO()
    writer = csv.writer(output, quoting=csv.QUOTE_MINIMAL)
    writer.writerow([
        "Subject",
        "Start Date",
        "Start Time",
        "End Date",
        "End Time",
        "All Day Event",
        "Description",
        "Location",
        "Private"
    ])

    current_year = datetime.now().year
    years_to_project = [current_year + i for i in range(project_upcoming_years)] if project_upcoming_years > 1 else [None]

    for ev in deduped:
        dt = ev["date"]
        etype = ev["type"]
        ename = ev["name"]
        tname = TYPE_NAMES.get(etype, "Událost")

        if etype == 0:
            base_desc = f"Narozeniny: {ename} (rok narození {dt.year})"
        elif etype == 1:
            base_desc = f"Výročí: {ename} (od roku {dt.year})"
        elif etype == 4:
            base_desc = f"Svátek: {ename}"
        else:
            base_desc = f"{tname}: {ename} (záznam z roku {dt.year})"

        if project_upcoming_years > 1 and etype != 3:
            for yr in years_to_project:
                try:
                    occ_dt = dt.replace(year=yr)
                except ValueError:
                    occ_dt = dt.replace(year=yr, day=28)

                age = yr - dt.year
                if etype == 0 and age >= 0:
                    desc = f"{base_desc} - {age}. narozeniny"
                elif etype == 1 and age >= 0:
                    desc = f"{base_desc} - {age}. výročí"
                else:
                    desc = base_desc

                d_str = occ_dt.strftime("%m/%d/%Y")
                writer.writerow([ename, d_str, "", d_str, "", "True", desc, "", "False"])
        else:
            d_str = dt.strftime("%m/%d/%Y")
            writer.writerow([ename, d_str, "", d_str, "", "True", base_desc, "", "False"])

    return output.getvalue()

def main():
    import argparse
    parser = argparse.ArgumentParser(description="Convert OKsoftware .imp files to iCalendar (.ics) and Google Calendar CSV")
    parser.add_argument("inputs", nargs="+", help="Files (.imp) or directories")
    parser.add_argument("-o", "--output", help="Output file path (.ics or .csv)")
    parser.add_argument("--format", choices=["ics", "csv"], default="ics", help="Output format (default: ics)")
    parser.add_argument("--name", default="Svátky a výročí", help="Calendar name (X-WR-CALNAME)")
    parser.add_argument("--project-years", type=int, default=5, help="Number of upcoming years to project in CSV (default: 5)")

    args = parser.parse_args()

    files = []
    for p in args.inputs:
        if os.path.isdir(p):
            files.extend(glob.glob(os.path.join(p, "**", "*.imp"), recursive=True))
        else:
            files.append(p)

    all_events = []
    for f in sorted(files):
        evs = parse_imp(f)
        all_events.extend(evs)

    fmt = args.format
    if args.output:
        if args.output.lower().endswith(".csv"):
            fmt = "csv"
        elif args.output.lower().endswith(".ics"):
            fmt = "ics"

    if fmt == "csv":
        content = events_to_csv(all_events, project_upcoming_years=args.project_years)
    else:
        content = events_to_ics(all_events, cal_name=args.name)

    if args.output:
        with open(args.output, 'w', encoding='utf-8') as f:
            f.write(content)
        print(f"Exported {len(all_events)} events -> {args.output} ({fmt.upper()})", file=sys.stderr)
    else:
        sys.stdout.write(content)

if __name__ == '__main__':
    main()