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use miette::{self, Diagnostic, NamedSource, SourceSpan};
use parol_runtime::{ParolError, TokenVec};
use thiserror::Error;

#[derive(Error, Diagnostic, Debug)]
pub enum ParserError {
    #[error("{cause}Expecting one of {expected_tokens}")]
    #[diagnostic(
        help("Syntax error in input prevents prediction of next production"),
        code(ParserError::UnexpectedToken)
    )]
    UnexpectedToken {
        cause: String,
        #[source_code]
        input: NamedSource,
        #[label("Error location")]
        error_location: SourceSpan,
        #[related("Unexpected tokens")]
        unexpected_tokens: Vec<UnexpectedToken>,
        expected_tokens: TokenVec,
        source: Option<anyhow::Error>,
    },

    #[error(transparent)]
    ParserError(#[from] parol_runtime::ParserError),

    #[error(transparent)]
    LexerError(#[from] parol_runtime::LexerError),

    #[error(transparent)]
    UserError(#[from] anyhow::Error),
}

#[derive(Error, Diagnostic, Debug)]
#[error("Unexpected token: {name} ({token_type})")]
#[diagnostic(help("Unexpected token"), code(parol_runtime::unexpected_token))]
pub struct UnexpectedToken {
    name: String,
    token_type: String,
    #[label("Unexpected token")]
    pub(crate) token: SourceSpan,
}

impl From<ParolError> for ParserError {
    fn from(x: ParolError) -> ParserError {
        match x {
            ParolError::ParserError(x) => match x {
                parol_runtime::ParserError::PredictionErrorWithExpectations {
                    cause,
                    input,
                    error_location,
                    unexpected_tokens,
                    expected_tokens,
                    source,
                } => ParserError::UnexpectedToken {
                    cause,
                    input: FileSource(input).into(),
                    error_location: Location(error_location).into(),
                    unexpected_tokens: UnexpectedTokens(unexpected_tokens).into(),
                    expected_tokens,
                    source: source.map(|x| x.into()),
                },
                _ => ParserError::ParserError(x),
            },
            ParolError::LexerError(x) => ParserError::LexerError(x),
            ParolError::UserError(x) => ParserError::UserError(x),
        }
    }
}

struct FileSource(parol_runtime::FileSource);

impl miette::SourceCode for FileSource {
    fn read_span<'a>(
        &'a self,
        span: &SourceSpan,
        context_lines_before: usize,
        context_lines_after: usize,
    ) -> Result<Box<dyn miette::SpanContents<'a> + 'a>, miette::MietteError> {
        <str as miette::SourceCode>::read_span(
            &self.0.input,
            span,
            context_lines_before,
            context_lines_after,
        )
    }
}

impl From<FileSource> for NamedSource {
    fn from(file_source: FileSource) -> Self {
        let file_name = file_source.0.file_name.clone();
        let file_name = file_name.to_str().unwrap_or("<Bad file name>");
        Self::new(file_name, file_source)
    }
}

struct Location(parol_runtime::Location);

impl From<Location> for SourceSpan {
    fn from(location: Location) -> Self {
        SourceSpan::new(
            (location.0.scanner_switch_pos + location.0.offset - location.0.length).into(),
            location.0.length.into(),
        )
    }
}

struct UnexpectedTokens(Vec<parol_runtime::UnexpectedToken>);

impl From<UnexpectedTokens> for Vec<UnexpectedToken> {
    fn from(value: UnexpectedTokens) -> Self {
        value
            .0
            .into_iter()
            .map(|v| UnexpectedToken {
                name: v.name,
                token_type: v.token_type,
                token: Location(v.token).into(),
            })
            .collect::<Vec<UnexpectedToken>>()
    }
}