use std::num::{ParseFloatError, ParseIntError};

use miette::Diagnostic;
use nom::error::{ContextError, ErrorKind, FromExternalError, ParseError};
use thiserror::Error;

#[cfg(doc)]
use {
    crate::KdlNode,
    std::convert::{TryFrom, TryInto},
};

/// An error that occurs when parsing a KDL document.
#[derive(Debug, Diagnostic, Clone, Eq, PartialEq, Error)]
#[error("Error parsing document: {kind}")]
#[diagnostic(code("{kind.code()}"))]
pub struct KdlError {
    pub input: String,
    /// Offset in chars of the error.
    pub offset: usize,
    pub kind: KdlErrorKind,
}

/// A type reprenting additional information specific to the type of error being returned.
#[derive(Debug, Clone, Eq, PartialEq, Error)]
pub enum KdlErrorKind {
    #[error(transparent)]
    ParseIntError(ParseIntError),
    #[error(transparent)]
    ParseFloatError(ParseFloatError),
    #[error("Failed to parse `{0}` component.")]
    Context(&'static str),
    #[error("An unspecified error occurred.")]
    Other,
}

/// Coversion errors for converting [`KdlNode`] to another type via [`TryFrom`] or [`TryInto`].
#[derive(Debug, Clone, Eq, PartialEq, Error)]
#[error("Failed to convert from KdlNodeValue::{variant} to {expected}.")]
pub struct TryFromKdlNodeValueError {
    pub(crate) expected: &'static str,
    pub(crate) variant: &'static str,
}

#[derive(Debug, Clone, Eq, PartialEq)]
pub(crate) struct KdlParseError<I> {
    pub(crate) input: I,
    pub(crate) context: Option<&'static str>,
    pub(crate) kind: Option<KdlErrorKind>,
}

impl<I> ParseError<I> for KdlParseError<I> {
    fn from_error_kind(input: I, _kind: nom::error::ErrorKind) -> Self {
        Self {
            input,
            context: None,
            kind: None,
        }
    }

    fn append(_input: I, _kind: nom::error::ErrorKind, other: Self) -> Self {
        other
    }
}

impl<I> ContextError<I> for KdlParseError<I> {
    fn add_context(_input: I, ctx: &'static str, mut other: Self) -> Self {
        other.context = Some(ctx);
        other
    }
}

impl<'a> FromExternalError<&'a str, ParseIntError> for KdlParseError<&'a str> {
    fn from_external_error(input: &'a str, _kind: ErrorKind, e: ParseIntError) -> Self {
        KdlParseError {
            input,
            context: None,
            kind: Some(KdlErrorKind::ParseIntError(e)),
        }
    }
}

impl<'a> FromExternalError<&'a str, ParseFloatError> for KdlParseError<&'a str> {
    fn from_external_error(input: &'a str, _kind: ErrorKind, e: ParseFloatError) -> Self {
        KdlParseError {
            input,
            context: None,
            kind: Some(KdlErrorKind::ParseFloatError(e)),
        }
    }
}