#!/usr/bin/env python3
from __future__ import annotations

import json
import sys
from datetime import date, datetime, time, timedelta
from pathlib import Path

from openpyxl import Workbook
from openpyxl.styles import Alignment, Border, Font, PatternFill, Side
from openpyxl.utils import get_column_letter


CONFIG_FILE = Path("config.json")


def parse_date(value: str) -> date:
    return datetime.strptime(value, "%Y-%m-%d").date()


def parse_time(value: str) -> time:
    return datetime.strptime(value, "%H:%M").time()


def get_monday(any_day: date) -> date:
    return any_day - timedelta(days=any_day.weekday())


def load_config(path: Path) -> dict:
    if not path.exists():
        raise FileNotFoundError(f"Missing config file: {path}")

    with path.open("r", encoding="utf-8") as handle:
        data = json.load(handle)

    required_keys = ["start_time", "end_time", "slot_minutes", "crews"]
    for key in required_keys:
        if key not in data:
            raise ValueError(f"config.json is missing '{key}'")

    crews = data["crews"]
    if not isinstance(crews, list) or not crews:
        raise ValueError("'crews' must be a non-empty array")

    clean_crews: list[str] = []
    for crew in crews:
        if not isinstance(crew, str):
            raise ValueError("Each crew name must be a string")

        crew_name = crew.strip()
        if not crew_name:
            raise ValueError("Crew names cannot be empty")

        clean_crews.append(crew_name)

    slot_minutes = int(data["slot_minutes"])
    if slot_minutes <= 0:
        raise ValueError("'slot_minutes' must be greater than zero")

    return {
        "start_time": parse_time(data["start_time"]),
        "end_time": parse_time(data["end_time"]),
        "slot_minutes": slot_minutes,
        "crews": clean_crews,
    }


def generate_time_slots(start: time, end: time, slot_minutes: int) -> list[str]:
    start_dt = datetime.combine(date.today(), start)
    end_dt = datetime.combine(date.today(), end)

    if end_dt <= start_dt:
        raise ValueError("'end_time' must be later than 'start_time'")

    slots: list[str] = []
    current = start_dt

    while current < end_dt:
        next_slot = current + timedelta(minutes=slot_minutes)
        slots.append(
            f"{current.strftime('%I:%M %p')} - {next_slot.strftime('%I:%M %p')}"
        )
        current = next_slot

    return slots


def apply_page_setup(worksheet) -> None:
    worksheet.page_setup.orientation = "landscape"
    worksheet.page_setup.fitToWidth = 1
    worksheet.page_setup.fitToHeight = 0
    worksheet.print_options.horizontalCentered = True
    worksheet.sheet_view.showGridLines = False
    worksheet.freeze_panes = "B4"


def style_sheet(worksheet, schedule_date: date, crews: list[str], time_slots: list[str]) -> None:
    thin_side = Side(style="thin", color="000000")
    border = Border(left=thin_side, right=thin_side, top=thin_side, bottom=thin_side)

    title_fill = PatternFill(fill_type="solid", fgColor="D9EAF7")
    header_fill = PatternFill(fill_type="solid", fgColor="EDEDED")

    title_font = Font(size=18, bold=True)
    header_font = Font(size=11, bold=True)
    cell_font = Font(size=10)

    center = Alignment(horizontal="center", vertical="center", wrap_text=True)
    top_wrap = Alignment(horizontal="left", vertical="top", wrap_text=True)

    sheet_title = schedule_date.strftime("%A").upper()
    sheet_date = schedule_date.strftime("%B %d, %Y")

    last_col = 1 + len(crews)
    last_col_letter = get_column_letter(last_col)

    worksheet.merge_cells(f"A1:{last_col_letter}1")
    worksheet["A1"] = f"{sheet_title} - {sheet_date}"
    worksheet["A1"].font = title_font
    worksheet["A1"].alignment = center
    worksheet["A1"].fill = title_fill
    worksheet["A1"].border = border
    worksheet.row_dimensions[1].height = 28

    worksheet["A3"] = "Time Slot"
    worksheet["A3"].font = header_font
    worksheet["A3"].alignment = center
    worksheet["A3"].fill = header_fill
    worksheet["A3"].border = border

    for crew_index, crew_name in enumerate(crews, start=2):
        cell = worksheet.cell(row=3, column=crew_index)
        cell.value = crew_name
        cell.font = header_font
        cell.alignment = center
        cell.fill = header_fill
        cell.border = border

    worksheet.column_dimensions["A"].width = 18

    for crew_index in range(2, last_col + 1):
        worksheet.column_dimensions[get_column_letter(crew_index)].width = 28

    row_index = 4
    for slot in time_slots:
        time_cell = worksheet.cell(row=row_index, column=1)
        time_cell.value = slot
        time_cell.font = header_font
        time_cell.alignment = center
        time_cell.border = border

        for crew_index in range(2, last_col + 1):
            cell = worksheet.cell(row=row_index, column=crew_index)
            cell.value = ""
            cell.font = cell_font
            cell.alignment = top_wrap
            cell.border = border

        worksheet.row_dimensions[row_index].height = 70
        row_index += 1

    apply_page_setup(worksheet)


def build_workbook(monday: date, crews: list[str], time_slots: list[str]) -> Workbook:
    workbook = Workbook()
    default_sheet = workbook.active
    workbook.remove(default_sheet)

    for day_offset in range(5):
        schedule_date = monday + timedelta(days=day_offset)
        sheet_name = schedule_date.strftime("%A")
        worksheet = workbook.create_sheet(title=sheet_name)
        style_sheet(worksheet, schedule_date, crews, time_slots)

    return workbook


def main() -> int:
    try:
        input_date = parse_date(sys.argv[1]) if len(sys.argv) > 1 else date.today()
        monday = get_monday(input_date)

        config = load_config(CONFIG_FILE)
        time_slots = generate_time_slots(
            config["start_time"],
            config["end_time"],
            config["slot_minutes"],
        )

        workbook = build_workbook(monday, config["crews"], time_slots)

        output_path = Path(f"weekly_schedule_{monday.isoformat()}.xlsx")
        workbook.save(output_path)

        print(f"Created: {output_path.resolve()}")
        return 0

    except Exception as exc:
        print(f"Error: {exc}", file=sys.stderr)
        return 1


if __name__ == "__main__":
    raise SystemExit(main())