//! Computational utility functions.

use std::cmp::Ordering;
use std::str::FromStr;

use super::prelude::*;
use crate::eval::Array;

/// Ensure that a condition is fulfilled.
pub fn assert(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v, span } = args.expect::<Spanned<bool>>("condition")?;
    if !v {
        bail!(span, "assertion failed");
    }
    Ok(Value::None)
}

/// The name of a value's type.
pub fn type_(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    Ok(args.expect::<Value>("value")?.type_name().into())
}

/// The string representation of a value.
pub fn repr(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    Ok(args.expect::<Value>("value")?.repr().into())
}

/// Join a sequence of values, optionally interspersing it with another value.
pub fn join(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let span = args.span;
    let sep = args.named::<Value>("sep")?.unwrap_or(Value::None);

    let mut result = Value::None;
    let mut iter = args.all::<Value>();

    if let Some(first) = iter.next() {
        result = first;
    }

    for value in iter {
        result = result.join(sep.clone()).at(span)?;
        result = result.join(value).at(span)?;
    }

    Ok(result)
}

/// Convert a value to a integer.
pub fn int(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v, span } = args.expect("value")?;
    Ok(Value::Int(match v {
        Value::Bool(v) => v as i64,
        Value::Int(v) => v,
        Value::Float(v) => v as i64,
        Value::Str(v) => match v.parse() {
            Ok(v) => v,
            Err(_) => bail!(span, "invalid integer"),
        },
        v => bail!(span, "cannot convert {} to integer", v.type_name()),
    }))
}

/// Convert a value to a float.
pub fn float(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v, span } = args.expect("value")?;
    Ok(Value::Float(match v {
        Value::Int(v) => v as f64,
        Value::Float(v) => v,
        Value::Str(v) => match v.parse() {
            Ok(v) => v,
            Err(_) => bail!(span, "invalid float"),
        },
        v => bail!(span, "cannot convert {} to float", v.type_name()),
    }))
}

/// Try to convert a value to a string.
pub fn str(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v, span } = args.expect("value")?;
    Ok(Value::Str(match v {
        Value::Int(v) => format_eco!("{}", v),
        Value::Float(v) => format_eco!("{}", v),
        Value::Str(v) => v,
        v => bail!(span, "cannot convert {} to string", v.type_name()),
    }))
}

/// Create an RGB(A) color.
pub fn rgb(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    Ok(Value::from(
        if let Some(string) = args.find::<Spanned<EcoString>>() {
            match RgbaColor::from_str(&string.v) {
                Ok(color) => color,
                Err(_) => bail!(string.span, "invalid hex string"),
            }
        } else {
            struct Component(u8);

            castable! {
                Component,
                Expected: "integer or relative",
                Value::Int(v) => match v {
                    0 ..= 255 => Self(v as u8),
                    _ => Err("must be between 0 and 255")?,
                },
                Value::Relative(v) => if (0.0 ..= 1.0).contains(&v.get()) {
                    Self((v.get() * 255.0).round() as u8)
                } else {
                    Err("must be between 0% and 100%")?
                },
            }

            let Component(r) = args.expect("red component")?;
            let Component(g) = args.expect("green component")?;
            let Component(b) = args.expect("blue component")?;
            let Component(a) = args.eat()?.unwrap_or(Component(255));
            RgbaColor::new(r, g, b, a)
        },
    ))
}
/// Create an CMYK color.
pub fn cmyk(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    struct Component(u8);

    castable! {
        Component,
        Expected: "relative",
        Value::Relative(v) => if (0.0 ..= 1.0).contains(&v.get()) {
            Self((v.get() * 255.0).round() as u8)
        } else {
            Err("must be between 0% and 100%")?
        },
    }

    let Component(c) = args.expect("cyan component")?;
    let Component(m) = args.expect("magenta component")?;
    let Component(y) = args.expect("yellow component")?;
    let Component(k) = args.expect("key component")?;
    Ok(Value::Color(CmykColor::new(c, m, y, k).into()))
}

/// The absolute value of a numeric value.
pub fn abs(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v, span } = args.expect("numeric value")?;
    Ok(match v {
        Value::Int(v) => Value::Int(v.abs()),
        Value::Float(v) => Value::Float(v.abs()),
        Value::Length(v) => Value::Length(v.abs()),
        Value::Angle(v) => Value::Angle(v.abs()),
        Value::Relative(v) => Value::Relative(v.abs()),
        Value::Fractional(v) => Value::Fractional(v.abs()),
        Value::Linear(_) => bail!(span, "cannot take absolute value of a linear"),
        v => bail!(span, "expected numeric value, found {}", v.type_name()),
    })
}

/// The minimum of a sequence of values.
pub fn min(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    minmax(args, Ordering::Less)
}

/// The maximum of a sequence of values.
pub fn max(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    minmax(args, Ordering::Greater)
}

/// Whether an integer is even.
pub fn even(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    Ok(Value::Bool(args.expect::<i64>("integer")? % 2 == 0))
}

/// Whether an integer is odd.
pub fn odd(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    Ok(Value::Bool(args.expect::<i64>("integer")? % 2 != 0))
}

/// The modulo of two numbers.
pub fn modulo(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v: v1, span: span1 } = args.expect("integer or float")?;
    let Spanned { v: v2, span: span2 } = args.expect("integer or float")?;

    let (a, b) = match (v1, v2) {
        (Value::Int(a), Value::Int(b)) => match a.checked_rem(b) {
            Some(res) => return Ok(Value::Int(res)),
            None => bail!(span2, "divisor must not be zero"),
        },
        (Value::Int(a), Value::Float(b)) => (a as f64, b),
        (Value::Float(a), Value::Int(b)) => (a, b as f64),
        (Value::Float(a), Value::Float(b)) => (a, b),
        (Value::Int(_), b) | (Value::Float(_), b) => bail!(
            span2,
            format!("expected integer or float, found {}", b.type_name())
        ),
        (a, _) => bail!(
            span1,
            format!("expected integer or float, found {}", a.type_name())
        ),
    };

    if b == 0.0 {
        bail!(span2, "divisor must not be zero");
    }

    Ok(Value::Float(a % b))
}

/// Find the minimum or maximum of a sequence of values.
fn minmax(args: &mut Args, goal: Ordering) -> TypResult<Value> {
    let mut extremum = args.expect::<Value>("value")?;
    for Spanned { v, span } in args.all::<Spanned<Value>>() {
        match v.partial_cmp(&extremum) {
            Some(ordering) => {
                if ordering == goal {
                    extremum = v;
                }
            }
            None => bail!(
                span,
                "cannot compare {} with {}",
                extremum.type_name(),
                v.type_name(),
            ),
        }
    }
    Ok(extremum)
}

/// Create a sequence of numbers.
pub fn range(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let first = args.expect::<i64>("end")?;
    let (start, end) = match args.eat::<i64>()? {
        Some(second) => (first, second),
        None => (0, first),
    };

    let step: i64 = match args.named("step")? {
        Some(Spanned { v: 0, span }) => bail!(span, "step must not be zero"),
        Some(Spanned { v, .. }) => v,
        None => 1,
    };

    let mut x = start;
    let mut seq = vec![];

    while x.cmp(&end) == 0.cmp(&step) {
        seq.push(Value::Int(x));
        x += step;
    }

    Ok(Value::Array(Array::from_vec(seq)))
}

/// Convert a string to lowercase.
pub fn lower(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    Ok(args.expect::<EcoString>("string")?.to_lowercase().into())
}

/// Convert a string to uppercase.
pub fn upper(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    Ok(args.expect::<EcoString>("string")?.to_uppercase().into())
}

/// Converts an integer into a roman numeral.
///
/// Works for integer between 0 and 3,999,999 inclusive, returns None otherwise.
/// Adapted from Yann Villessuzanne's roman.rs under the Unlicense, at
/// https://github.com/linfir/roman.rs/
pub fn roman(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    static PAIRS: &'static [(&'static str, usize)] = &[
        ("M̅", 1000000),
        ("D̅", 500000),
        ("C̅", 100000),
        ("L̅", 50000),
        ("X̅", 10000),
        ("V̅", 5000),
        ("I̅V̅", 4000),
        ("M", 1000),
        ("CM", 900),
        ("D", 500),
        ("CD", 400),
        ("C", 100),
        ("XC", 90),
        ("L", 50),
        ("XL", 40),
        ("X", 10),
        ("IX", 9),
        ("V", 5),
        ("IV", 4),
        ("I", 1),
    ];

    let Spanned { mut v, span } = args.expect("non-negative integer")?;
    match v {
        0_usize => return Ok("N".into()),
        3_999_999 .. => {
            bail!(
                span,
                "cannot convert integers greater than 3,999,999 to roman numerals"
            )
        }
        _ => {}
    }

    let mut roman = String::new();
    for &(name, value) in PAIRS {
        while v >= value {
            v -= value;
            roman.push_str(name);
        }
    }

    Ok(roman.into())
}

/// Convert a number into a roman numeral.
pub fn symbol(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    static SYMBOLS: &'static [char] = &['*', '†', '‡', '§', '‖', '¶'];

    let n = args.expect::<usize>("non-negative integer")?;

    let symbol = SYMBOLS[n % SYMBOLS.len()];
    let amount = (n / SYMBOLS.len()) + 1;

    let symbols: String = std::iter::repeat(symbol).take(amount).collect();
    Ok(symbols.into())
}

/// The length of a string, an array or a dictionary.
pub fn len(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v, span } = args.expect("collection")?;
    Ok(Value::Int(match v {
        Value::Str(v) => v.len() as i64,
        Value::Array(v) => v.len(),
        Value::Dict(v) => v.len(),
        v => bail!(
            span,
            "expected string, array or dictionary, found {}",
            v.type_name(),
        ),
    }))
}

/// The sorted version of an array.
pub fn sorted(_: &mut EvalContext, args: &mut Args) -> TypResult<Value> {
    let Spanned { v, span } = args.expect::<Spanned<Array>>("array")?;
    Ok(Value::Array(v.sorted().at(span)?))
}