use std::collections::HashMap;

#[cfg(feature = "random")]
use num_traits::{One, Signed, ToPrimitive, Zero};
#[cfg(feature = "random")]
use rand::Rng;

use super::Builtin;
use crate::unit::Unit;
use crate::value::{Number, Value};

pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
    f.insert(
        "percentage".to_owned(),
        Builtin::new(|mut args, scope, super_selector| {
            max_args!(args, 1);
            let num = match arg!(args, scope, super_selector, 0, "number") {
                Value::Dimension(n, Unit::None) => n * Number::from(100),
                v @ Value::Dimension(..) => {
                    return Err((
                        format!(
                            "$number: Expected {} to have no units.",
                            v.to_css_string(args.span())?
                        ),
                        args.span(),
                    )
                        .into())
                }
                v => {
                    return Err((
                        format!(
                            "$number: {} is not a number.",
                            v.to_css_string(args.span())?
                        ),
                        args.span(),
                    )
                        .into())
                }
            };
            Ok(Value::Dimension(num, Unit::Percent))
        }),
    );
    f.insert(
        "round".to_owned(),
        Builtin::new(|mut args, scope, super_selector| {
            max_args!(args, 1);
            match arg!(args, scope, super_selector, 0, "number") {
                Value::Dimension(n, u) => Ok(Value::Dimension(n.round(), u)),
                v => Err((
                    format!(
                        "$number: {} is not a number.",
                        v.to_css_string(args.span())?
                    ),
                    args.span(),
                )
                    .into()),
            }
        }),
    );
    f.insert(
        "ceil".to_owned(),
        Builtin::new(|mut args, scope, super_selector| {
            max_args!(args, 1);
            match arg!(args, scope, super_selector, 0, "number") {
                Value::Dimension(n, u) => Ok(Value::Dimension(n.ceil(), u)),
                v => Err((
                    format!(
                        "$number: {} is not a number.",
                        v.to_css_string(args.span())?
                    ),
                    args.span(),
                )
                    .into()),
            }
        }),
    );
    f.insert(
        "floor".to_owned(),
        Builtin::new(|mut args, scope, super_selector| {
            max_args!(args, 1);
            match arg!(args, scope, super_selector, 0, "number") {
                Value::Dimension(n, u) => Ok(Value::Dimension(n.floor(), u)),
                v => Err((
                    format!(
                        "$number: {} is not a number.",
                        v.to_css_string(args.span())?
                    ),
                    args.span(),
                )
                    .into()),
            }
        }),
    );
    f.insert(
        "abs".to_owned(),
        Builtin::new(|mut args, scope, super_selector| {
            max_args!(args, 1);
            match arg!(args, scope, super_selector, 0, "number") {
                Value::Dimension(n, u) => Ok(Value::Dimension(n.abs(), u)),
                v => Err((
                    format!(
                        "$number: {} is not a number.",
                        v.to_css_string(args.span())?
                    ),
                    args.span(),
                )
                    .into()),
            }
        }),
    );
    f.insert(
        "comparable".to_owned(),
        Builtin::new(|mut args, scope, super_selector| {
            max_args!(args, 2);
            let unit1 = match arg!(args, scope, super_selector, 0, "number1") {
                Value::Dimension(_, u) => u,
                v => {
                    return Err((
                        format!(
                            "$number1: {} is not a number.",
                            v.to_css_string(args.span())?
                        ),
                        args.span(),
                    )
                        .into())
                }
            };
            let unit2 = match arg!(args, scope, super_selector, 1, "number2") {
                Value::Dimension(_, u) => u,
                v => {
                    return Err((
                        format!(
                            "$number2: {} is not a number.",
                            v.to_css_string(args.span())?
                        ),
                        args.span(),
                    )
                        .into())
                }
            };

            Ok(Value::bool(unit1.comparable(&unit2)))
        }),
    );
    // TODO: write tests for this. how?
    #[cfg(feature = "random")]
    f.insert(
        "random".to_owned(),
        Builtin::new(|mut args, scope, super_selector| {
            max_args!(args, 1);
            let limit = match arg!(args, scope, super_selector, 0, "limit" = Value::Null) {
                Value::Dimension(n, _) => n,
                Value::Null => {
                    let mut rng = rand::thread_rng();
                    return Ok(Value::Dimension(
                        Number::from(rng.gen_range(0.0, 1.0)),
                        Unit::None,
                    ));
                }
                v => {
                    return Err((
                        format!("$limit: {} is not a number.", v.to_css_string(args.span())?),
                        args.span(),
                    )
                        .into())
                }
            };

            if limit.is_one() {
                return Ok(Value::Dimension(Number::one(), Unit::None));
            }

            if limit.is_decimal() {
                return Err((format!("$limit: {} is not an int.", limit), args.span()).into());
            }

            if limit.is_zero() || limit.is_negative() {
                return Err((
                    format!("$limit: Must be greater than 0, was {}.", limit),
                    args.span(),
                )
                    .into());
            }

            let limit = match limit.to_integer().to_u32() {
                Some(n) => n,
                None => {
                    return Err((
                        format!("max must be in range 0 < max ≤ 2^32, was {}", limit),
                        args.span(),
                    )
                        .into())
                }
            };

            let mut rng = rand::thread_rng();
            Ok(Value::Dimension(
                Number::from(rng.gen_range(0, limit) + 1),
                Unit::None,
            ))
        }),
    );
}