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use syn::{
    parse::{Parse, ParseStream},
    punctuated::Punctuated,
    Ident, Token,
};

use crate::{DurationError, DurationHuman, DurationHumanValidator};

impl Parse for DurationHumanValidator {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let parser = Punctuated::<ParsedDuration, Token![,]>::parse_separated_nonempty;
        let durations: Vec<ParsedDuration> = parser(input)?.into_iter().collect();
        let result = durations.try_into();
        match result {
            Ok(result) => Ok(result),
            Err(err) => Err(input.error(err)),
        }
    }
}

struct ParsedDuration {
    arg: DurationRangeArgument,
    duration: DurationHuman,
}

enum DurationRangeArgument {
    Min,
    Default,
    Max,
}

impl Parse for DurationRangeArgument {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let name: Ident = input.parse()?;
        let name = name.to_string();
        match name.as_str() {
            "min" => Ok(Self::Min),
            "max" => Ok(Self::Max),
            "default" => Ok(Self::Default),

            _ => Err(input.error(format!(
                "duration argument '{}' not recognized, use min, max and default",
                name
            ))),
        }
    }
}

impl Parse for ParsedDuration {
    fn parse(input: ParseStream) -> syn::Result<Self> {
        let name: DurationRangeArgument = input.parse()?;
        let _punc: Token![:] = input.parse()?;
        let value: DurationHuman = input.parse()?;

        Ok(Self {
            arg: name,
            duration: value,
        })
    }
}

#[derive(Default)]
struct DurationRangeWithOptionalValues {
    min: Option<DurationHuman>,
    max: Option<DurationHuman>,
    default: Option<DurationHuman>,
}

impl From<Vec<ParsedDuration>> for DurationRangeWithOptionalValues {
    fn from(value: Vec<ParsedDuration>) -> Self {
        value.iter().fold(Self::default(), |mut y, x| {
            match x.arg {
                DurationRangeArgument::Min => y.min = Some(x.duration),
                DurationRangeArgument::Max => y.max = Some(x.duration),
                DurationRangeArgument::Default => y.default = Some(x.duration),
            }

            y
        })
    }
}

impl TryFrom<Vec<ParsedDuration>> for DurationHumanValidator {
    type Error = DurationError;

    fn try_from(value: Vec<ParsedDuration>) -> Result<Self, Self::Error> {
        let optionals: DurationRangeWithOptionalValues = value.into();
        optionals.min.map_or_else(
            || Err(DurationError::DurationValidationMinMustBeSpecified),
            |min| {
                optionals.max.map_or_else(
                    || Err(DurationError::DurationValidationMaxMustBeSpecified),
                    |max| {
                        optionals.default.map_or_else(
                            || Self::try_from((min, max)),
                            |default| Self::try_from((min, default, max)),
                        )
                    },
                )
            },
        )
    }
}