use crate::lexer::LexError;

use crate::token::Span;

use std::fmt;

use std::path::{Path, PathBuf};

use unicode_width::UnicodeWidthStr;

/// A convenience error type to tie together all the detailed errors produced by

/// this crate.

///

/// This type can be created from a [`LexError`]. This also contains

/// storage for file/text information so a nice error can be rendered along the

/// same lines of rustc's own error messages (minus the color).

///

/// This type is typically suitable for use in public APIs for consumers of this

/// crate.

#[derive(Debug)]

pub struct Error {

    inner: Box<ErrorInner>,

}

#[derive(Debug)]

struct ErrorInner {

    text: Option<Text>,

    file: Option<PathBuf>,

    span: Span,

    kind: ErrorKind,

}

#[derive(Debug)]

struct Text {

    line: usize,

    col: usize,

    snippet: String,

}

#[derive(Debug)]

enum ErrorKind {

    Lex(LexError),

    Custom(String),

}

impl Error {

    pub(crate) fn lex(span: Span, content: &str, kind: LexError) -> Error {

        let mut ret = Error {

            inner: Box::new(ErrorInner {

                text: None,

                file: None,

                span,

                kind: ErrorKind::Lex(kind),

            }),

        };

        ret.set_text(content);

        ret

    }

    pub(crate) fn parse(span: Span, content: &str, message: String) -> Error {

        let mut ret = Error {

            inner: Box::new(ErrorInner {

                text: None,

                file: None,

                span,

                kind: ErrorKind::Custom(message),

            }),

        };

        ret.set_text(content);

        ret

    }

    /// Creates a new error with the given `message` which is targeted at the

    /// given `span`

    ///

    /// Note that you'll want to ensure that `set_text` or `set_path` is called

    /// on the resulting error to improve the rendering of the error message.

    pub fn new(span: Span, message: String) -> Error {

        Error {

            inner: Box::new(ErrorInner {

                text: None,

                file: None,

                span,

                kind: ErrorKind::Custom(message),

            }),

        }

    }

    /// Return the `Span` for this error.

    pub fn span(&self) -> Span {

        self.inner.span

    }

    /// To provide a more useful error this function can be used to extract

    /// relevant textual information about this error into the error itself.

    ///

    /// The `contents` here should be the full text of the original file being

    /// parsed, and this will extract a sub-slice as necessary to render in the

    /// `Display` implementation later on.

    pub fn set_text(&mut self, contents: &str) {

        if self.inner.text.is_some() {

            return;

        }

        self.inner.text = Some(Text::new(contents, self.inner.span));

    }

    /// To provide a more useful error this function can be used to set

    /// the file name that this error is associated with.

    ///

    /// The `path` here will be stored in this error and later rendered in the

    /// `Display` implementation.

    pub fn set_path(&mut self, path: &Path) {

        if self.inner.file.is_some() {

            return;

        }

        self.inner.file = Some(path.to_path_buf());

    }

    /// Returns the underlying `LexError`, if any, that describes this error.

    pub fn lex_error(&self) -> Option<&LexError> {

        match &self.inner.kind {

            ErrorKind::Lex(e) => Some(e),

            _ => None,

        }

    }

    /// Returns the underlying message, if any, that describes this error.

    pub fn message(&self) -> String {

        match &self.inner.kind {

            ErrorKind::Lex(e) => e.to_string(),

            ErrorKind::Custom(e) => e.clone(),

        }

    }

}

impl fmt::Display for Error {

    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {

        let err = match &self.inner.kind {

            ErrorKind::Lex(e) => e as &dyn fmt::Display,

            ErrorKind::Custom(e) => e as &dyn fmt::Display,

        };

        let text = match &self.inner.text {

            Some(text) => text,

            None => {

                return write!(f, "{err} at byte offset {}", self.inner.span.offset);

            }

        };

        let file = self

            .inner

            .file

            .as_ref()

            .and_then(|p| p.to_str())

            .unwrap_or("<anon>");

        let col = text.col + 1;

        let line = text.line + 1;

        // If the column is too big skip the fancy rendering below and just

        // print the raw error.

        if col > 500 {

            return write!(f, "{err} at {file}:{line}:{col}");

        }

        write!(

            f,

            "\

{err}

     --> {file}:{line}:{col}

      |

 {line:4} | {text}

      | {marker:>0$}",

            col,

            text = text.snippet,

            marker = "^",

        )

    }

}

impl std::error::Error for Error {}

impl Text {

    fn new(content: &str, span: Span) -> Text {

        let (line, col) = span.linecol_in(content);

        let contents = content.lines().nth(line).unwrap_or("");

        let mut snippet = String::new();

        for ch in contents.chars() {

            match ch {

                // Replace tabs with spaces to render consistently

                '\t' => {

                    snippet.push_str("    ");

                }

                // these codepoints change how text is rendered so for clarity

                // in error messages they're dropped.

                '\u{202a}' | '\u{202b}' | '\u{202d}' | '\u{202e}' | '\u{2066}' | '\u{2067}'

                | '\u{2068}' | '\u{206c}' | '\u{2069}' => {}

                c => snippet.push(c),

            }

        }

        // Use the `unicode-width` crate to figure out how wide the snippet, up

        // to our "column", actually is. That'll tell us how many spaces to

        // place before the `^` character that points at the problem

        let col = snippet.get(..col).map(|s| s.width()).unwrap_or(col);

        Text { line, col, snippet }

    }

}