use crate::commands::WholeStreamCommand;
use crate::prelude::*;
use nu_errors::ShellError;
use nu_protocol::{
    ColumnPath, Primitive, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value,
};
use nu_source::Tagged;
use num_bigint::{BigInt, BigUint, ToBigInt};

// TODO num_format::SystemLocale once platform-specific dependencies are stable (see Cargo.toml)
use num_format::{Locale, ToFormattedString};
use num_traits::{Pow, Signed};
use std::iter;

pub struct SubCommand;

#[derive(Deserialize)]
struct Arguments {
    rest: Vec<ColumnPath>,
    decimals: Option<Tagged<u64>>,
    #[serde(rename(deserialize = "group-digits"))]
    group_digits: bool,
}

#[async_trait]
impl WholeStreamCommand for SubCommand {
    fn name(&self) -> &str {
        "str from"
    }

    fn signature(&self) -> Signature {
        Signature::build("str from")
            .rest(
                SyntaxShape::ColumnPath,
                "optionally convert to string by column paths",
            )
            .named(
                "decimals",
                SyntaxShape::Int,
                "decimal digits to which to round",
                Some('d'),
            )
            .switch(
                "group-digits",
                // TODO according to system localization
                "group digits, currently by thousand with commas",
                Some('g'),
            )
    }

    fn usage(&self) -> &str {
        "Converts numeric types to strings. Trims trailing zeros unless decimals parameter is specified."
    }

    async fn run(
        &self,
        args: CommandArgs,
        registry: &CommandRegistry,
    ) -> Result<OutputStream, ShellError> {
        operate(args, registry).await
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "round to nearest integer",
                example: "= 1.7 | str from -d 0",
                result: Some(vec![UntaggedValue::string("2").into_untagged_value()]),
            },
            Example {
                description: "format large number with localized digit grouping",
                example: "= 1000000.2 | str from -g",
                result: Some(vec![
                    UntaggedValue::string("1,000,000.2").into_untagged_value()
                ]),
            },
        ]
    }
}

async fn operate(
    args: CommandArgs,
    registry: &CommandRegistry,
) -> Result<OutputStream, ShellError> {
    let (
        Arguments {
            decimals,
            group_digits,
            rest: column_paths,
        },
        input,
    ) = args.process(&registry.clone()).await?;
    let digits = decimals.map(|tagged| tagged.item);

    Ok(input
        .map(move |v| {
            if column_paths.is_empty() {
                ReturnSuccess::value(action(&v, v.tag(), digits, group_digits)?)
            } else {
                let mut ret = v;
                for path in &column_paths {
                    ret = ret.swap_data_by_column_path(
                        path,
                        Box::new(move |old| action(old, old.tag(), digits, group_digits)),
                    )?;
                }

                ReturnSuccess::value(ret)
            }
        })
        .to_output_stream())
}

// TODO If you're using the with-system-locale feature and you're on Windows, Clang 3.9 or higher is also required.
fn action(
    input: &Value,
    tag: impl Into<Tag>,
    digits: Option<u64>,
    group_digits: bool,
) -> Result<Value, ShellError> {
    match &input.value {
        UntaggedValue::Primitive(prim) => Ok(UntaggedValue::string(match prim {
            Primitive::Int(int) => {
                if group_digits {
                    format_bigint(int) // int.to_formatted_string(*locale)
                } else {
                    int.to_string()
                }
            }
            Primitive::Decimal(dec) => format_decimal(dec.clone(), digits, group_digits),
            _ => {
                return Err(ShellError::unimplemented(
                    "str from for non-numeric primitives",
                ))
            }
        })
        .into_value(tag)),
        UntaggedValue::Row(_) => Err(ShellError::labeled_error(
            "specify column to use 'str from'",
            "found table",
            input.tag.clone(),
        )),
        _ => Err(ShellError::unimplemented(
            "str from for non-primitive, non-table types",
        )),
    }
}

fn format_bigint(int: &BigInt) -> String {
    int.to_formatted_string(&Locale::en)

    // TODO once platform-specific dependencies are stable (see Cargo.toml)
    // #[cfg(windows)]
    // {
    //     int.to_formatted_string(&Locale::en)
    // }
    // #[cfg(not(windows))]
    // {
    //     match SystemLocale::default() {
    //         Ok(locale) => int.to_formatted_string(&locale),
    //         Err(_) => int.to_formatted_string(&Locale::en),
    //     }
    // }
}

fn format_decimal(mut decimal: BigDecimal, digits: Option<u64>, group_digits: bool) -> String {
    if let Some(n) = digits {
        decimal = round_decimal(&decimal, n)
    }

    if decimal.is_integer() && (digits.is_none() || digits == Some(0)) {
        let int = decimal
            .to_bigint()
            .expect("integer BigDecimal should convert to BigInt");
        return if group_digits {
            int.to_string()
        } else {
            format_bigint(&int)
        };
    }

    let (int, exp) = decimal.as_bigint_and_exponent();
    let factor = BigInt::from(10).pow(BigUint::from(exp as u64)); // exp > 0 for non-int decimal
    let int_part = &int / &factor;
    let dec_part = (&int % &factor)
        .abs()
        .to_biguint()
        .expect("BigInt::abs should always produce positive signed BigInt and thus BigUInt")
        .to_str_radix(10);

    let dec_str = if let Some(n) = digits {
        dec_part
            .chars()
            .chain(iter::repeat('0'))
            .take(n as usize)
            .collect()
    } else {
        String::from(dec_part.trim_end_matches('0'))
    };

    let format_default_loc = |int_part: BigInt| {
        let loc = Locale::en;
        let (int_str, sep) = (
            int_part.to_formatted_string(&loc),
            String::from(loc.decimal()),
        );

        format!("{}{}{}", int_str, sep, dec_str)
    };

    format_default_loc(int_part)

    // TODO once platform-specific dependencies are stable (see Cargo.toml)
    // #[cfg(windows)]
    // {
    //     format_default_loc(int_part)
    // }
    // #[cfg(not(windows))]
    // {
    //     match SystemLocale::default() {
    //         Ok(sys_loc) => {
    //             let int_str = int_part.to_formatted_string(&sys_loc);
    //             let sep = String::from(sys_loc.decimal());
    //             format!("{}{}{}", int_str, sep, dec_str)
    //         }
    //         Err(_) => format_default_loc(int_part),
    //     }
    // }
}

fn round_decimal(decimal: &BigDecimal, mut digits: u64) -> BigDecimal {
    let mut mag = decimal.clone();
    while mag >= BigDecimal::from(1) {
        mag = mag / 10;
        digits += 1;
    }

    decimal.with_prec(digits)
}

#[cfg(test)]
mod tests {
    use super::SubCommand;

    #[test]
    fn examples_work_as_expected() {
        use crate::examples::test as test_examples;

        test_examples(SubCommand {})
    }
}