//! Miscellaneous tools to format and parse numbers, durations, etc.
//!
//! TODO(emilk): move some of this numeric formatting into `emath` so we can use it in `egui_plot`.

mod time;

use std::{cmp::PartialOrd, fmt::Display};

pub use time::next_grid_tick_magnitude_ns;

// --- Numbers ---

/// The minus character: <https://www.compart.com/en/unicode/U+2212>
///
/// Looks slightly different from the normal hyphen `-`.
const MINUS: char = '−';

// TODO(rust-num/num-traits#315): waiting for https://github.com/rust-num/num-traits/issues/315 to land
pub trait UnsignedAbs {
    /// An unsigned type which is large enough to hold the absolute value of `Self`.
    type Unsigned;

    /// Computes the absolute value of `self` without any wrapping or panicking.
    fn unsigned_abs(self) -> Self::Unsigned;
}

impl UnsignedAbs for i8 {
    type Unsigned = u8;

    #[inline]
    fn unsigned_abs(self) -> Self::Unsigned {
        self.unsigned_abs()
    }
}

impl UnsignedAbs for i16 {
    type Unsigned = u16;

    #[inline]
    fn unsigned_abs(self) -> Self::Unsigned {
        self.unsigned_abs()
    }
}

impl UnsignedAbs for i32 {
    type Unsigned = u32;

    #[inline]
    fn unsigned_abs(self) -> Self::Unsigned {
        self.unsigned_abs()
    }
}

impl UnsignedAbs for i64 {
    type Unsigned = u64;

    #[inline]
    fn unsigned_abs(self) -> Self::Unsigned {
        self.unsigned_abs()
    }
}

impl UnsignedAbs for i128 {
    type Unsigned = u128;

    #[inline]
    fn unsigned_abs(self) -> Self::Unsigned {
        self.unsigned_abs()
    }
}

impl UnsignedAbs for isize {
    type Unsigned = usize;

    #[inline]
    fn unsigned_abs(self) -> Self::Unsigned {
        self.unsigned_abs()
    }
}

/// Pretty format a signed number by using thousands separators for readability.
///
/// The returned value is for human eyes only, and can not be parsed
/// by the normal `usize::from_str` function.
pub fn format_int<Int>(number: Int) -> String
where
    Int: Display + PartialOrd + num_traits::Zero + UnsignedAbs,
    Int::Unsigned: Display + num_traits::Unsigned,
{
    if number < Int::zero() {
        format!("{MINUS}{}", format_uint(number.unsigned_abs()))
    } else {
        add_thousands_separators(&number.to_string())
    }
}

/// Pretty format an unsigned integer by using thousands separators for readability.
///
/// The returned value is for human eyes only, and can not be parsed
/// by the normal `usize::from_str` function.
#[allow(clippy::needless_pass_by_value)]
pub fn format_uint<Uint>(number: Uint) -> String
where
    Uint: Display + num_traits::Unsigned,
{
    add_thousands_separators(&number.to_string())
}

/// Add thousands separators to a number, every three steps,
/// counting from the last character.
fn add_thousands_separators(number: &str) -> String {
    let mut chars = number.chars().rev().peekable();

    let mut result = vec![];
    while chars.peek().is_some() {
        if !result.is_empty() {
            // thousands-deliminator:
            let thin_space = '\u{2009}'; // https://en.wikipedia.org/wiki/Thin_space
            result.push(thin_space);
        }
        for _ in 0..3 {
            if let Some(c) = chars.next() {
                result.push(c);
            }
        }
    }

    result.reverse();
    result.into_iter().collect()
}

#[test]
fn test_format_uint() {
    assert_eq!(format_uint(42_u32), "42");
    assert_eq!(format_uint(999_u32), "999");
    assert_eq!(format_uint(1_000_u32), "1 000");
    assert_eq!(format_uint(123_456_u32), "123 456");
    assert_eq!(format_uint(1_234_567_u32), "1 234 567");
}

/// Options for how to format a floating point number, e.g. an [`f64`].
#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
pub struct FloatFormatOptions {
    /// Always show the sign, even if it is positive (`+`).
    pub always_sign: bool,

    /// Maximum digits of precision to use.
    ///
    /// This includes both the integer part and the fractional part.
    pub precision: usize,

    /// Max number of decimals to show after the decimal point.
    ///
    /// If not specified, [`Self::precision`] is used instead.
    pub num_decimals: Option<usize>,

    pub strip_trailing_zeros: bool,
}

impl FloatFormatOptions {
    /// Default options for formatting an [`f32`].
    #[allow(non_upper_case_globals)]
    pub const DEFAULT_f32: Self = Self {
        always_sign: false,
        precision: 7,
        num_decimals: None,
        strip_trailing_zeros: true,
    };

    /// Default options for formatting an [`f64`].
    #[allow(non_upper_case_globals)]
    pub const DEFAULT_f64: Self = Self {
        always_sign: false,
        precision: 15,
        num_decimals: None,
        strip_trailing_zeros: true,
    };

    /// Always show the sign, even if it is positive (`+`).
    #[inline]
    pub fn with_always_sign(mut self, always_sign: bool) -> Self {
        self.always_sign = always_sign;
        self
    }

    /// Show at most this many digits of precision,
    /// including both the integer part and the fractional part.
    #[inline]
    pub fn with_precision(mut self, precision: usize) -> Self {
        self.precision = precision;
        self
    }

    /// Max number of decimals to show after the decimal point.
    ///
    /// If not specified, [`Self::precision`] is used instead.
    #[inline]
    pub fn with_decimals(mut self, num_decimals: usize) -> Self {
        self.num_decimals = Some(num_decimals);
        self
    }

    /// Strip trailing zeros from decimal expansion?
    #[inline]
    pub fn with_strip_trailing_zeros(mut self, strip_trailing_zeros: bool) -> Self {
        self.strip_trailing_zeros = strip_trailing_zeros;
        self
    }

    /// The returned value is for human eyes only, and can not be parsed
    /// by the normal `f64::from_str` function.
    pub fn format(&self, value: impl Into<f64>) -> String {
        self.format_f64(value.into())
    }

    fn format_f64(&self, mut value: f64) -> String {
        fn reverse(s: &str) -> String {
            s.chars().rev().collect()
        }

        let Self {
            always_sign,
            precision,
            num_decimals,
            strip_trailing_zeros,
        } = *self;

        if value.is_nan() {
            return "NaN".to_owned();
        }

        let sign = if value < 0.0 {
            value = -value;
            "−" // NOTE: the minus character: <https://www.compart.com/en/unicode/U+2212>
        } else if always_sign {
            "+"
        } else {
            ""
        };

        let abs_string = if value == f64::INFINITY {
            "∞".to_owned()
        } else {
            let magnitude = value.log10();
            let max_decimals = precision as f64 - magnitude.max(0.0);

            if max_decimals < 0.0 {
                // A very large number (more digits than we have precision),
                // so use scientific notation.
                // TODO(emilk): nice formatting of scientific notation with thousands separators
                format!("{:.*e}", precision.saturating_sub(1), value)
            } else {
                let max_decimals = max_decimals as usize;

                let num_decimals = if let Some(num_decimals) = num_decimals {
                    num_decimals.min(max_decimals)
                } else {
                    max_decimals
                };

                let mut formatted = format!("{value:.num_decimals$}");

                if strip_trailing_zeros && formatted.contains('.') {
                    while formatted.ends_with('0') {
                        formatted.pop();
                    }
                    if formatted.ends_with('.') {
                        formatted.pop();
                    }
                }

                if let Some(dot) = formatted.find('.') {
                    let integer_part = &formatted[..dot];
                    let fractional_part = &formatted[dot + 1..];
                    // let fractional_part = &fractional_part[..num_decimals.min(fractional_part.len())];

                    let integer_part = add_thousands_separators(integer_part);
                    // For the fractional part we should start counting thousand separators from the _front_, so we reverse:
                    let fractional_part =
                        reverse(&add_thousands_separators(&reverse(fractional_part)));
                    format!("{integer_part}.{fractional_part}")
                } else {
                    add_thousands_separators(&formatted) // it's an integer
                }
            }
        };

        format!("{sign}{abs_string}")
    }
}

/// Format a number with about 15 decimals of precision.
///
/// The returned value is for human eyes only, and can not be parsed
/// by the normal `f64::from_str` function.
pub fn format_f64(value: f64) -> String {
    FloatFormatOptions::DEFAULT_f64.format(value)
}

/// Format a number with about 7 decimals of precision.
///
/// The returned value is for human eyes only, and can not be parsed
/// by the normal `f64::from_str` function.
pub fn format_f32(value: f32) -> String {
    FloatFormatOptions::DEFAULT_f32.format(value)
}

#[test]
fn test_format_f32() {
    let cases = [
        (f32::NAN, "NaN"),
        (f32::INFINITY, "∞"),
        (f32::NEG_INFINITY, "−∞"),
        (0.0, "0"),
        (42.0, "42"),
        (10_000.0, "10 000"),
        (1_000_000.0, "1 000 000"),
        (10_000_000.0, "10 000 000"),
        (11_000_000.0, "1.100000e7"),
        (-42.0, "−42"),
        (-4.20, "−4.2"),
        (123_456.78, "123 456.8"),
        (78.4321, "78.432 1"),
        (-std::f32::consts::PI, "−3.141 593"),
        (-std::f32::consts::PI * 1e6, "−3 141 593"),
        (-std::f32::consts::PI * 1e20, "−3.141593e20"), // We switch to scientific notation to not show false precision
    ];
    for (value, expected) in cases {
        let got = format_f32(value);
        assert!(
            got == expected,
            "Expected to format {value} as '{expected}', but got '{got}'"
        );
    }
}

#[test]
fn test_format_f64() {
    let cases = [
        (f64::NAN, "NaN"),
        (f64::INFINITY, "∞"),
        (f64::NEG_INFINITY, "−∞"),
        (0.0, "0"),
        (42.0, "42"),
        (-42.0, "−42"),
        (-4.20, "−4.2"),
        (123_456_789.0, "123 456 789"),
        (123_456_789.123_45, "123 456 789.123 45"),
        (0.0000123456789, "0.000 012 345 678 9"),
        (0.123456789, "0.123 456 789"),
        (1.23456789, "1.234 567 89"),
        (12.3456789, "12.345 678 9"),
        (123.456789, "123.456 789"),
        (1234.56789, "1 234.567 89"),
        (12345.6789, "12 345.678 9"),
        (78.4321, "78.432 1"),
        (-std::f64::consts::PI, "−3.141 592 653 589 79"),
        (-std::f64::consts::PI * 1e6, "−3 141 592.653 589 79"),
        (-std::f64::consts::PI * 1e20, "−3.14159265358979e20"), // We switch to scientific notation to not show false precision
    ];
    for (value, expected) in cases {
        let got = format_f64(value);
        assert!(
            got == expected,
            "Expected to format {value} as '{expected}', but got '{got}'"
        );
    }
}

#[test]
fn test_format_f64_custom() {
    let cases = [(
        FloatFormatOptions::DEFAULT_f64.with_decimals(2),
        123.456789,
        "123.46",
    )];
    for (options, value, expected) in cases {
        let got = options.format(value);
        assert!(
            got == expected,
            "Expected to format {value} as '{expected}', but got '{got}'. Options: {options:#?}"
        );
    }
}

/// Pretty format a large number by using SI notation (base 10), e.g.
///
/// ```
/// # use re_format::approximate_large_number;
/// assert_eq!(approximate_large_number(123 as _), "123");
/// assert_eq!(approximate_large_number(12_345 as _), "12k");
/// assert_eq!(approximate_large_number(1_234_567 as _), "1.2M");
/// assert_eq!(approximate_large_number(123_456_789 as _), "123M");
/// ```
///
/// Prefer to use [`format_uint`], which outputs an exact string,
/// while still being readable thanks to half-width spaces used as thousands-separators.
pub fn approximate_large_number(number: f64) -> String {
    if number < 0.0 {
        format!("{MINUS}{}", approximate_large_number(-number))
    } else if number < 1000.0 {
        format!("{number:.0}")
    } else if number < 1_000_000.0 {
        let decimals = (number < 10_000.0) as usize;
        format!("{:.*}k", decimals, number / 1_000.0)
    } else if number < 1_000_000_000.0 {
        let decimals = (number < 10_000_000.0) as usize;
        format!("{:.*}M", decimals, number / 1_000_000.0)
    } else {
        let decimals = (number < 10_000_000_000.0) as usize;
        format!("{:.*}G", decimals, number / 1_000_000_000.0)
    }
}

#[test]
fn test_format_large_number() {
    let test_cases = [
        (999.0, "999"),
        (1000.0, "1.0k"),
        (1001.0, "1.0k"),
        (999_999.0, "1000k"),
        (1_000_000.0, "1.0M"),
        (999_999_999.0, "1000M"),
        (1_000_000_000.0, "1.0G"),
        (999_999_999_999.0, "1000G"),
        (1_000_000_000_000.0, "1000G"),
        (123.0, "123"),
        (12_345.0, "12k"),
        (1_234_567.0, "1.2M"),
        (123_456_789.0, "123M"),
    ];

    for (value, expected) in test_cases {
        assert_eq!(expected, approximate_large_number(value));
    }
}

// --- Bytes ---

/// Pretty format a number of bytes by using SI notation (base2), e.g.
///
/// ```
/// # use re_format::format_bytes;
/// assert_eq!(format_bytes(123.0), "123 B");
/// assert_eq!(format_bytes(12_345.0), "12.1 KiB");
/// assert_eq!(format_bytes(1_234_567.0), "1.2 MiB");
/// assert_eq!(format_bytes(123_456_789.0), "118 MiB");
/// ```
pub fn format_bytes(number_of_bytes: f64) -> String {
    if number_of_bytes < 0.0 {
        format!("{MINUS}{}", format_bytes(-number_of_bytes))
    } else if number_of_bytes < 10.0_f64.exp2() {
        format!("{number_of_bytes:.0} B")
    } else if number_of_bytes < 20.0_f64.exp2() {
        let decimals = (10.0 * number_of_bytes < 20.0_f64.exp2()) as usize;
        format!("{:.*} KiB", decimals, number_of_bytes / 10.0_f64.exp2())
    } else if number_of_bytes < 30.0_f64.exp2() {
        let decimals = (10.0 * number_of_bytes < 30.0_f64.exp2()) as usize;
        format!("{:.*} MiB", decimals, number_of_bytes / 20.0_f64.exp2())
    } else {
        let decimals = (10.0 * number_of_bytes < 40.0_f64.exp2()) as usize;
        format!("{:.*} GiB", decimals, number_of_bytes / 30.0_f64.exp2())
    }
}

#[test]
fn test_format_bytes() {
    let test_cases = [
        (999.0, "999 B"),
        (1000.0, "1000 B"),
        (1001.0, "1001 B"),
        (1023.0, "1023 B"),
        (1024.0, "1.0 KiB"),
        (1025.0, "1.0 KiB"),
        (1024.0 * 1.2345, "1.2 KiB"),
        (1024.0 * 12.345, "12.3 KiB"),
        (1024.0 * 123.45, "123 KiB"),
        (1024f64.powi(2) - 1.0, "1024 KiB"),
        (1024f64.powi(2) + 0.0, "1.0 MiB"),
        (1024f64.powi(2) + 1.0, "1.0 MiB"),
        (1024f64.powi(3) - 1.0, "1024 MiB"),
        (1024f64.powi(3) + 0.0, "1.0 GiB"),
        (1024f64.powi(3) + 1.0, "1.0 GiB"),
        (1.2345 * 30.0_f64.exp2(), "1.2 GiB"),
        (12.345 * 30.0_f64.exp2(), "12.3 GiB"),
        (123.45 * 30.0_f64.exp2(), "123 GiB"),
        (1024f64.powi(4) - 1.0, "1024 GiB"),
        (1024f64.powi(4) + 0.0, "1024 GiB"),
        (1024f64.powi(4) + 1.0, "1024 GiB"),
        (123.0, "123 B"),
        (12_345.0, "12.1 KiB"),
        (1_234_567.0, "1.2 MiB"),
        (123_456_789.0, "118 MiB"),
    ];

    for (value, expected) in test_cases {
        assert_eq!(format_bytes(value), expected);
    }
}

pub fn parse_bytes_base10(bytes: &str) -> Option<i64> {
    // Note: intentionally case sensitive so that we don't parse `Mb` (Megabit) as `MB` (Megabyte).
    if let Some(rest) = bytes.strip_prefix(MINUS) {
        Some(-parse_bytes_base10(rest)?)
    } else if let Some(kb) = bytes.strip_suffix("kB") {
        Some(kb.parse::<i64>().ok()? * 1_000)
    } else if let Some(mb) = bytes.strip_suffix("MB") {
        Some(mb.parse::<i64>().ok()? * 1_000_000)
    } else if let Some(gb) = bytes.strip_suffix("GB") {
        Some(gb.parse::<i64>().ok()? * 1_000_000_000)
    } else if let Some(tb) = bytes.strip_suffix("TB") {
        Some(tb.parse::<i64>().ok()? * 1_000_000_000_000)
    } else if let Some(b) = bytes.strip_suffix('B') {
        Some(b.parse::<i64>().ok()?)
    } else {
        None
    }
}

#[test]
fn test_parse_bytes_base10() {
    let test_cases = [
        ("999B", 999),
        ("1000B", 1_000),
        ("1kB", 1_000),
        ("1000kB", 1_000_000),
        ("1MB", 1_000_000),
        ("1000MB", 1_000_000_000),
        ("1GB", 1_000_000_000),
        ("1000GB", 1_000_000_000_000),
        ("1TB", 1_000_000_000_000),
        ("1000TB", 1_000_000_000_000_000),
        ("123B", 123),
        ("12kB", 12_000),
        ("123MB", 123_000_000),
        ("-10B", -10), // hyphen-minus
        ("−10B", -10), // proper minus
    ];
    for (value, expected) in test_cases {
        assert_eq!(Some(expected), parse_bytes_base10(value));
    }
}

pub fn parse_bytes_base2(bytes: &str) -> Option<i64> {
    // Note: intentionally case sensitive so that we don't parse `Mib` (Mebibit) as `MiB` (Mebibyte).
    if let Some(rest) = bytes.strip_prefix(MINUS) {
        Some(-parse_bytes_base2(rest)?)
    } else if let Some(kb) = bytes.strip_suffix("KiB") {
        Some(kb.parse::<i64>().ok()? * 1024)
    } else if let Some(mb) = bytes.strip_suffix("MiB") {
        Some(mb.parse::<i64>().ok()? * 1024 * 1024)
    } else if let Some(gb) = bytes.strip_suffix("GiB") {
        Some(gb.parse::<i64>().ok()? * 1024 * 1024 * 1024)
    } else if let Some(tb) = bytes.strip_suffix("TiB") {
        Some(tb.parse::<i64>().ok()? * 1024 * 1024 * 1024 * 1024)
    } else if let Some(b) = bytes.strip_suffix('B') {
        Some(b.parse::<i64>().ok()?)
    } else {
        None
    }
}

#[test]
fn test_parse_bytes_base2() {
    let test_cases = [
        ("999B", 999),
        ("1023B", 1_023),
        ("1024B", 1_024),
        ("1KiB", 1_024),
        ("1000KiB", 1_000 * 1024),
        ("1MiB", 1024 * 1024),
        ("1000MiB", 1_000 * 1024 * 1024),
        ("1GiB", 1024 * 1024 * 1024),
        ("1000GiB", 1_000 * 1024 * 1024 * 1024),
        ("1TiB", 1024 * 1024 * 1024 * 1024),
        ("1000TiB", 1_000 * 1024 * 1024 * 1024 * 1024),
        ("123B", 123),
        ("12KiB", 12 * 1024),
        ("123MiB", 123 * 1024 * 1024),
        ("-10B", -10), // hyphen-minus
        ("−10B", -10), // proper minus
    ];
    for (value, expected) in test_cases {
        assert_eq!(Some(expected), parse_bytes_base2(value));
    }
}

pub fn parse_bytes(bytes: &str) -> Option<i64> {
    parse_bytes_base10(bytes).or_else(|| parse_bytes_base2(bytes))
}

#[test]
fn test_parse_bytes() {
    let test_cases = [
        // base10
        ("999B", 999),
        ("1000B", 1_000),
        ("1kB", 1_000),
        ("1000kB", 1_000_000),
        ("1MB", 1_000_000),
        ("1000MB", 1_000_000_000),
        ("1GB", 1_000_000_000),
        ("1000GB", 1_000_000_000_000),
        ("1TB", 1_000_000_000_000),
        ("1000TB", 1_000_000_000_000_000),
        ("123B", 123),
        ("12kB", 12_000),
        ("123MB", 123_000_000),
        // base2
        ("999B", 999),
        ("1023B", 1_023),
        ("1024B", 1_024),
        ("1KiB", 1_024),
        ("1000KiB", 1_000 * 1024),
        ("1MiB", 1024 * 1024),
        ("1000MiB", 1_000 * 1024 * 1024),
        ("1GiB", 1024 * 1024 * 1024),
        ("1000GiB", 1_000 * 1024 * 1024 * 1024),
        ("1TiB", 1024 * 1024 * 1024 * 1024),
        ("1000TiB", 1_000 * 1024 * 1024 * 1024 * 1024),
        ("123B", 123),
        ("12KiB", 12 * 1024),
        ("123MiB", 123 * 1024 * 1024),
    ];
    for (value, expected) in test_cases {
        assert_eq!(Some(expected), parse_bytes(value));
    }
}

// --- Durations ---

pub fn parse_duration(duration: &str) -> Result<f32, String> {
    fn parse_num(s: &str) -> Result<f32, String> {
        s.parse()
            .map_err(|_ignored| format!("Expected a number, got {s:?}"))
    }

    if let Some(ms) = duration.strip_suffix("ms") {
        Ok(parse_num(ms)? * 1e-3)
    } else if let Some(s) = duration.strip_suffix('s') {
        Ok(parse_num(s)?)
    } else if let Some(s) = duration.strip_suffix('m') {
        Ok(parse_num(s)? * 60.0)
    } else if let Some(s) = duration.strip_suffix('h') {
        Ok(parse_num(s)? * 60.0 * 60.0)
    } else {
        Err(format!(
            "Expected a suffix of 'ms', 's', 'm' or 'h' in string {duration:?}"
        ))
    }
}

#[test]
fn test_parse_duration() {
    assert_eq!(parse_duration("3.2s"), Ok(3.2));
    assert_eq!(parse_duration("250ms"), Ok(0.250));
    assert_eq!(parse_duration("3m"), Ok(3.0 * 60.0));
}