Strftime

import type { DateLike, StrftimeOptions } from "../utils"

const REGEX_PARSE =
    /^(\d{4})[-/]?(\d{1,2})?[-/]?(\d{0,2})[Tt\s]*(\d{1,2})?:?(\d{1,2})?:?(\d{1,2})?[.:]?(\d+)?$/

const REGEX_FORMAT =
    /%S|%Y|%m|%d|%H|%M|%B|%b|%I|%-I|%p|%a|%A|%w|%y|%f|%z|%Z|%j|%U|%W|%c|%x|%X/g

/**
 * A helper function that formats a date object into a string.
 *
 * @param date - The date object to format.
 *
 * @param str - The format string.
 *
 * @returns The formatted date string.
 */
function format(date: Date, str: string, options: StrftimeOptions): string {
    const years = date.getFullYear()

    const month = date.getMonth()

    const days = date.getDate()

    const hours = date.getHours()

    const minutes = date.getMinutes()

    const seconds = date.getSeconds()

    const milliseconds = date.getMilliseconds()

    const matches: Record<string, () => string | string> = {
        "%a": () =>
            date.toLocaleDateString(options.locales, { weekday: "short" }),

        "%A": () =>
            date.toLocaleDateString(options.locales, { weekday: "long" }),

        "%w": () => String(date.getDay()),

        "%d": () => `${days}`.padStart(2, "0"),

        "%b": () =>
            date.toLocaleDateString(options.locales, { month: "short" }),

        "%B": () => date.toLocaleDateString(options.locales, { month: "long" }),

        "%m": () => `${month + 1}`.padStart(2, "0"),

        "%y": () => `${years}`.slice(-2),

        "%Y": () => `${years}`,

        "%H": () => `${hours}`,

        "%I": () => `${hours % 12 || 12}`.padStart(1, "0"),

        "%-I": () => `${hours % 12 || 12}`.padStart(2, "0"),

        "%p": () => (hours < 12 ? "AM" : "PM"),

        "%M": () => `${minutes}`.padStart(2, "0"),

        "%S": () => `${seconds}`.padStart(2, "0"),

        "%f": () => `${milliseconds}`.padStart(3, "0"),

        "%z": () => `${date}`.match(/([+-]\d{4})/)?.[1] || "",

        "%Z": () => `${date}`.match(/([A-Z]{3,5})/)?.[1] || "",

        "%j": () => {
            const start = new Date(years, 0, 0)
            const diff = date.getTime() - start.getTime()
            const day = 1000 * 60 * 60 * 24
            return String(Math.floor(diff / day)).padStart(3, "0")
        },
        "%U": () => {
            const start = new Date(years, 0, 0)
            const diff = date.getTime() - start.getTime()
            const one_day = 1000 * 60 * 60 * 24
            const day = start.getDay()
            return String(Math.floor((diff / one_day + day) / 7)).padStart(
                2,
                "0"
            )
        },
        "%W": () => {
            const start = new Date(years, 0, 0)
            const diff = date.getTime() - start.getTime()
            const one_day = 1000 * 60 * 60 * 24
            const day = start.getDay()
            return String(Math.floor((diff / one_day + day) / 7)).padStart(
                2,
                "0"
            )
        },
        "%c": () => {
            const _options = { ...options }

            delete _options.locales

            return date.toLocaleString(options.locales, _options)
        },
    }

    function matcher(match: string) {
        if (!matches[match]) return match

        return matches[match]()
    }

    return str.replace(REGEX_FORMAT, matcher)
}

/**
 * A helper function that parses a value into a date object.
 *
 * @param date - The value to parse.
 *
 * @returns The parsed date object.
 */
function parser(date: DateLike): Date {
    if (date === null) return new Date(NaN) // null is invalid

    if (date === undefined) return new Date()

    if (date instanceof Date) return new Date(date)

    if (typeof date === "string" && !/Z$/i.test(date)) {
        const d = date.match(REGEX_PARSE) as any

        if (d) {
            const m = d[2] - 1 || 0

            const ms = (d[7] || "0").substring(0, 3)

            return new Date(
                d[1],
                m,
                d[3] || 1,
                d[4] || 0,
                d[5] || 0,
                d[6] || 0,
                ms
            )
        }
    }

    return new Date(date)
}

/**
 * Formats a date for a given format string code
 *
 * @param date - The date to format
 *
 * @param str - The format string code
 *
 * @param options - The options to pass to the date formatter
 * - locales - The locales to use for formatting
 *  - DateTimeFormatOptions - The options to pass to the date formatter.
 *
 * @see https://docs.python.org/3/library/datetime.html#datetime.date.strftime
 *
 * @see  Format Codes: https://docs.python.org/3/library/datetime.html#strftime-and-strptime-format-codes
 */
export function strftime(
    date: DateLike,
    str: string,
    options: StrftimeOptions = {}
) {
    return format(parser(date), str, options)
}