// Copyright © 2024 Mikhail Hogrefe
//
// This file is part of Malachite.
//
// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.

use crate::chars::crement::increment_char;
use crate::chars::CharType;
use crate::comparison::traits::Min;
use core::ops::RangeInclusive;

/// Generates all ASCII [`char`]s, in ascending order.
///
/// For a friendlier order (_e.g_. nonprintable [`char`]s coming last), try
/// [`exhaustive_ascii_chars`].
///
/// The output length is 128.
///
/// # Complexity per iteration
/// Constant time and additional memory.
///
/// # Examples
/// ```
/// use malachite_base::chars::exhaustive::ascii_chars_increasing;
///
/// assert_eq!(
///     ascii_chars_increasing().collect::<String>(),
///     "\u{0}\u{1}\u{2}\u{3}\u{4}\u{5}\u{6}\u{7}\u{8}\t\n\u{b}\u{c}\r\u{e}\u{f}\u{10}\u{11}\u{12}\
///     \u{13}\u{14}\u{15}\u{16}\u{17}\u{18}\u{19}\u{1a}\u{1b}\u{1c}\u{1d}\u{1e}\u{1f} !\"#$%&\'()*\
///     +,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\u{7f}"
/// );
/// ```
pub const fn ascii_chars_increasing() -> RangeInclusive<char> {
    char::MIN..='\u{7f}'
}

/// Generates all [`char`]s, in ascending order.
///
/// For a friendlier order (_e.g_. nonprintable [`char`]s coming last), try [`exhaustive_chars`].
///
/// The output length is 1,112,064.
///
/// # Complexity per iteration
/// Constant time and additional memory.
///
/// # Examples
/// ```
/// use malachite_base::chars::exhaustive::chars_increasing;
///
/// assert_eq!(
///     chars_increasing().take(200).collect::<String>(),
///     "\u{0}\u{1}\u{2}\u{3}\u{4}\u{5}\u{6}\u{7}\u{8}\t\n\u{b}\u{c}\r\u{e}\u{f}\u{10}\u{11}\u{12}\
///     \u{13}\u{14}\u{15}\u{16}\u{17}\u{18}\u{19}\u{1a}\u{1b}\u{1c}\u{1d}\u{1e}\u{1f} !\"#$%&\'()*\
///     +,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\u{7f}\
///     \u{80}\u{81}\u{82}\u{83}\u{84}\u{85}\u{86}\u{87}\u{88}\u{89}\u{8a}\u{8b}\u{8c}\u{8d}\u{8e}\
///     \u{8f}\u{90}\u{91}\u{92}\u{93}\u{94}\u{95}\u{96}\u{97}\u{98}\u{99}\u{9a}\u{9b}\u{9c}\u{9d}\
///     \u{9e}\u{9f}\u{a0}¡¢£¤¥¦§¨©ª«¬\u{ad}®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇ"
/// );
/// ```
pub const fn chars_increasing() -> RangeInclusive<char> {
    char::MIN..=char::MAX
}

/// Generates all [`char`]s, in a friendly order, so that more familiar [`char`] come first.
///
/// The order is
/// - Lowercase ASCII letters,
/// - Uppercase ASCII letters,
/// - ASCII digits,
/// - Graphic ASCII [`char`]s (not alphanumeric and not control), including `' '` but no other
///   whitespace,
/// - (only if `ascii_only` is false) Graphic Non-ASCII [`char`]s; all non-ASCII [`char`]s whose
///   [`Debug`](std::fmt::Debug) representations don't start with `'\'`,
/// - All remaining [`char`]s.
///
/// This `struct` is created by [`exhaustive_chars`] and [`exhaustive_ascii_chars`]; see their
/// documentation for more.
#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
pub struct ExhaustiveChars {
    ascii_only: bool,
    first: bool,
    c: char,
    current_type: CharType,
}

impl Iterator for ExhaustiveChars {
    type Item = char;

    fn next(&mut self) -> Option<char> {
        if self.first {
            self.first = false;
        } else {
            match self.current_type {
                CharType::AsciiLower => {
                    if self.c == 'z' {
                        self.current_type = CharType::AsciiUpper;
                        self.c = 'A';
                    } else {
                        increment_char(&mut self.c);
                    }
                }
                CharType::AsciiUpper => {
                    if self.c == 'Z' {
                        self.current_type = CharType::AsciiNumeric;
                        self.c = '0';
                    } else {
                        increment_char(&mut self.c);
                    }
                }
                CharType::AsciiNumeric => {
                    if self.c == '9' {
                        self.current_type = CharType::AsciiNonAlphanumericGraphic;
                        self.c = ' ';
                    } else {
                        increment_char(&mut self.c);
                    }
                }
                CharType::AsciiNonAlphanumericGraphic => {
                    if self.c == '~' {
                        if self.ascii_only {
                            self.current_type = CharType::NonGraphic;
                            self.c = '\0';
                        } else {
                            self.current_type = CharType::NonAsciiGraphic;
                            self.c = '\u{a1}';
                        };
                    } else {
                        increment_char(&mut self.c);
                        // No control chars between ' ' and '~'
                        while self.c.is_ascii_alphanumeric() {
                            increment_char(&mut self.c);
                        }
                    }
                }
                CharType::NonAsciiGraphic => {
                    if self.c == '\u{323af}' {
                        self.current_type = CharType::NonGraphic;
                        self.c = '\0';
                    } else {
                        increment_char(&mut self.c);
                        while !CharType::NonAsciiGraphic.contains(self.c) {
                            increment_char(&mut self.c);
                        }
                    }
                }
                CharType::NonGraphic => {
                    let limit = if self.ascii_only { '\u{7f}' } else { char::MAX };
                    if self.c == limit {
                        return None;
                    }
                    increment_char(&mut self.c);
                    while !self.c.is_ascii_control()
                        && (self.c.is_ascii() || CharType::NonAsciiGraphic.contains(self.c))
                    {
                        increment_char(&mut self.c);
                    }
                }
            }
        }
        Some(self.c)
    }
}

/// Generates all ASCII [`char`]s, in a friendly order, so that more familiar [`char`]s come first.
///
/// The order is
/// - Lowercase ASCII letters,
/// - Uppercase ASCII letters,
/// - ASCII digits,
/// - Graphic ASCII [`char`]s (not alphanumeric and not control), including `' '` but no other
///   whitespace,
/// - All remaining ASCII [`char`]s.
///
/// Within each group, the [`char`]s are ordered according to their usual order.
///
/// If you want to generate ASCII [`char`]s in their usual order, try [`ascii_chars_increasing`].
///
/// The output length is 128.
///
/// # Complexity per iteration
/// Constant time and additional memory.
///
/// # Examples
/// ```
/// use malachite_base::chars::exhaustive::exhaustive_ascii_chars;
///
/// assert_eq!(
///     exhaustive_ascii_chars().collect::<String>(),
///     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 !\"#$%&\'()*+,-./:;<=>?@[\\\
///     ]^_`{|}~\u{0}\u{1}\u{2}\u{3}\u{4}\u{5}\u{6}\u{7}\u{8}\t\n\u{b}\u{c}\r\u{e}\u{f}\u{10}\u{11}\
///     \u{12}\u{13}\u{14}\u{15}\u{16}\u{17}\u{18}\u{19}\u{1a}\u{1b}\u{1c}\u{1d}\u{1e}\u{1f}\u{7f}"
/// );
/// ```
pub const fn exhaustive_ascii_chars() -> ExhaustiveChars {
    ExhaustiveChars {
        ascii_only: true,
        first: true,
        c: 'a',
        current_type: CharType::AsciiLower,
    }
}

/// Generates all [`char`]s, in a friendly order, so that more familiar [`char`]s come first.
///
/// The order is
/// - Lowercase ASCII letters,
/// - Uppercase ASCII letters,
/// - ASCII digits,
/// - Graphic ASCII [`char`] (not alphanumeric and not control), including `' '` but no other
///   whitespace,
/// - Graphic Non-ASCII [`char`]s; all non-ASCII [`char`]s whose [`Debug`](std::fmt::Debug)
///   representations don't start with `'\'`,
/// - All remaining [`char`]s.
///
/// Within each group, the [`char`]s are ordered according to their usual order.
///
/// If you want to generate [`char`]s in their usual order, try [`chars_increasing`].
///
/// The output length is 1,112,064.
///
/// # Complexity per iteration
/// Constant time and additional memory.
///
/// # Examples
/// ```
/// use malachite_base::chars::exhaustive::exhaustive_chars;
///
/// assert_eq!(
///     exhaustive_chars().take(200).collect::<String>(),
///     "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 !\"#$%&\'()*+,-./:;<=>?@[\\\
///     ]^_`{|}~¡¢£¤¥¦§¨©ª«¬®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóô\
///     õö÷øùúûüýþÿĀāĂ㥹ĆćĈĉĊ"
/// );
/// ```
pub const fn exhaustive_chars() -> ExhaustiveChars {
    ExhaustiveChars {
        ascii_only: false,
        first: true,
        c: 'a',
        current_type: CharType::AsciiLower,
    }
}