use std::fmt;

use crate::{TextRange, TextUnit};

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct SyntaxError {
    kind: SyntaxErrorKind,
    location: Location,
}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum Location {
    Offset(TextUnit),
    Range(TextRange),
}

impl Into<Location> for TextUnit {
    fn into(self) -> Location {
        Location::Offset(self)
    }
}

impl Into<Location> for TextRange {
    fn into(self) -> Location {
        Location::Range(self)
    }
}

impl SyntaxError {
    pub fn new<L: Into<Location>>(kind: SyntaxErrorKind, loc: L) -> SyntaxError {
        SyntaxError {
            kind,
            location: loc.into(),
        }
    }

    pub fn kind(&self) -> SyntaxErrorKind {
        self.kind.clone()
    }

    pub fn location(&self) -> Location {
        self.location.clone()
    }

    pub fn offset(&self) -> TextUnit {
        match self.location {
            Location::Offset(offset) => offset,
            Location::Range(range) => range.start(),
        }
    }

    pub fn add_offset(mut self, plus_offset: TextUnit) -> SyntaxError {
        self.location = match self.location {
            Location::Range(range) => Location::Range(range + plus_offset),
            Location::Offset(offset) => Location::Offset(offset + plus_offset),
        };

        self
    }
}

impl fmt::Display for SyntaxError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        self.kind.fmt(f)
    }
}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum SyntaxErrorKind {
    ParseError(ParseError),
    UnescapedCodepoint,
    EmptyChar,
    UnclosedChar,
    LongChar,
    EmptyAsciiEscape,
    InvalidAsciiEscape,
    TooShortAsciiCodeEscape,
    AsciiCodeEscapeOutOfRange,
    MalformedAsciiCodeEscape,
    UnclosedUnicodeEscape,
    MalformedUnicodeEscape,
    EmptyUnicodeEcape,
    OverlongUnicodeEscape,
    UnicodeEscapeOutOfRange,
}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct ParseError(pub String);

impl fmt::Display for SyntaxErrorKind {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        use self::SyntaxErrorKind::*;
        match self {
            UnescapedCodepoint => write!(f, "This codepoint should always be escaped"),
            EmptyAsciiEscape => write!(f, "Empty escape sequence"),
            InvalidAsciiEscape => write!(f, "Invalid escape sequence"),
            EmptyChar => write!(f, "Empty char literal"),
            UnclosedChar => write!(f, "Unclosed char literal"),
            LongChar => write!(f, "Char literal should be one character long"),
            TooShortAsciiCodeEscape => write!(f, "Escape sequence should have two digits"),
            AsciiCodeEscapeOutOfRange => {
                write!(f, "Escape sequence should be between \\x00 and \\x7F")
            }
            MalformedAsciiCodeEscape => write!(f, "Escape sequence should be a hexadecimal number"),
            UnclosedUnicodeEscape => write!(f, "Missing `}}`"),
            MalformedUnicodeEscape => write!(f, "Malformed unicode escape sequence"),
            EmptyUnicodeEcape => write!(f, "Empty unicode escape sequence"),
            OverlongUnicodeEscape => {
                write!(f, "Unicode escape sequence should have at most 6 digits")
            }
            UnicodeEscapeOutOfRange => write!(f, "Unicode escape code should be at most 0x10FFFF"),
            ParseError(msg) => write!(f, "{}", msg.0),
        }
    }
}