use std::{
    fmt,
    io::{self, Read, Write},
};

use rbx_dom_weak::types::VariantType;

/// An error that can occur when deserializing an XML-format model or place.
#[derive(Debug)]
pub struct DecodeError {
    // This indirection drops the size of the error type substantially (~150
    // bytes to 8 on 64-bit), which is important since it's passed around every
    // function!
    inner: Box<DecodeErrorImpl>,
}

impl DecodeError {
    pub(crate) fn new_from_reader<R: Read>(
        kind: DecodeErrorKind,
        reader: &xml::EventReader<R>,
    ) -> DecodeError {
        use xml::common::Position;

        let pos = reader.position();

        DecodeError {
            inner: Box::new(DecodeErrorImpl {
                kind,
                line: (pos.row + 1) as usize,
                column: pos.column as usize,
            }),
        }
    }

    /// 1-based line number in the document where the error occured.
    pub fn line(&self) -> usize {
        self.inner.line
    }

    /// 1-based column number in the document where the error occured.
    pub fn column(&self) -> usize {
        self.inner.column
    }
}

impl fmt::Display for DecodeError {
    fn fmt(&self, output: &mut fmt::Formatter) -> fmt::Result {
        write!(
            output,
            "line {}, column {}: {}",
            self.inner.line, self.inner.column, self.inner.kind
        )
    }
}

impl std::error::Error for DecodeError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        self.inner.kind.source()
    }
}

#[derive(Debug)]
struct DecodeErrorImpl {
    kind: DecodeErrorKind,
    line: usize,
    column: usize,
}

#[derive(Debug)]
pub(crate) enum DecodeErrorKind {
    // Errors from other crates
    Xml(xml::reader::Error),
    ParseFloat(std::num::ParseFloatError),
    ParseInt(std::num::ParseIntError),
    DecodeBase64(base64::DecodeError),

    // Errors specific to rbx_xml
    WrongDocVersion(String),
    UnexpectedEof,
    UnexpectedXmlEvent(xml::reader::XmlEvent),
    MissingAttribute(&'static str),
    UnknownProperty {
        class_name: String,
        property_name: String,
    },
    InvalidContent(&'static str),
    NameMustBeString(VariantType),
    UnsupportedPropertyConversion {
        class_name: String,
        property_name: String,
        expected_type: VariantType,
        actual_type: VariantType,
        message: String,
    },
}

impl fmt::Display for DecodeErrorKind {
    fn fmt(&self, output: &mut fmt::Formatter) -> fmt::Result {
        use self::DecodeErrorKind::*;

        match self {
            Xml(err) => write!(output, "{}", err),
            ParseFloat(err) => write!(output, "{}", err),
            ParseInt(err) => write!(output, "{}", err),
            DecodeBase64(err) => write!(output, "{}", err),

            WrongDocVersion(version) => {
                write!(output, "Invalid version '{}', expected version 4", version)
            }
            UnexpectedEof => write!(output, "Unexpected end-of-file"),
            UnexpectedXmlEvent(event) => write!(output, "Unexpected XML event {:?}", event),
            MissingAttribute(attribute_name) => {
                write!(output, "Missing attribute '{}'", attribute_name)
            }
            UnknownProperty {
                class_name,
                property_name,
            } => write!(
                output,
                "Property {}.{} is unknown",
                class_name, property_name
            ),
            InvalidContent(explain) => write!(output, "Invalid text content: {}", explain),
            NameMustBeString(ty) => write!(
                output,
                "The 'Name' property must be of type String, but it was {:?}",
                ty
            ),
            UnsupportedPropertyConversion {
                class_name,
                property_name,
                expected_type,
                actual_type,
                message,
            } => write!(
                output,
                "Property {}.{} is expected to be of type {:?}, but it was of type {:?} \
                 When trying to convert, this error occured: {}",
                class_name, property_name, expected_type, actual_type, message
            ),
        }
    }
}

impl std::error::Error for DecodeErrorKind {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        use self::DecodeErrorKind::*;

        match self {
            Xml(err) => Some(err),
            ParseFloat(err) => Some(err),
            ParseInt(err) => Some(err),
            DecodeBase64(err) => Some(err),

            WrongDocVersion(_)
            | UnexpectedEof
            | UnexpectedXmlEvent(_)
            | MissingAttribute(_)
            | UnknownProperty { .. }
            | InvalidContent(_)
            | NameMustBeString(_)
            | UnsupportedPropertyConversion { .. } => None,
        }
    }
}

impl From<xml::reader::Error> for DecodeErrorKind {
    fn from(error: xml::reader::Error) -> DecodeErrorKind {
        DecodeErrorKind::Xml(error)
    }
}

impl From<std::num::ParseFloatError> for DecodeErrorKind {
    fn from(error: std::num::ParseFloatError) -> DecodeErrorKind {
        DecodeErrorKind::ParseFloat(error)
    }
}

impl From<std::num::ParseIntError> for DecodeErrorKind {
    fn from(error: std::num::ParseIntError) -> DecodeErrorKind {
        DecodeErrorKind::ParseInt(error)
    }
}

impl From<base64::DecodeError> for DecodeErrorKind {
    fn from(error: base64::DecodeError) -> DecodeErrorKind {
        DecodeErrorKind::DecodeBase64(error)
    }
}

/// An error that can occur when serializing an XML-format model or place.
#[derive(Debug)]
pub struct EncodeError {
    // This Box helps reduce the size of EncodeError a lot, which is important.
    kind: Box<EncodeErrorKind>,
}

impl EncodeError {
    pub(crate) fn new_from_writer<W: Write>(
        kind: EncodeErrorKind,
        _writer: &xml::EventWriter<W>,
    ) -> EncodeError {
        EncodeError {
            kind: Box::new(kind),
        }
    }
}

impl fmt::Display for EncodeError {
    fn fmt(&self, output: &mut fmt::Formatter) -> fmt::Result {
        write!(output, "{}", self.kind)
    }
}

impl std::error::Error for EncodeError {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        self.kind.source()
    }
}

#[derive(Debug)]
pub(crate) enum EncodeErrorKind {
    Io(io::Error),
    Xml(xml::writer::Error),

    UnknownProperty {
        class_name: String,
        property_name: String,
    },
    UnsupportedPropertyType(VariantType),
    UnsupportedPropertyConversion {
        class_name: String,
        property_name: String,
        expected_type: VariantType,
        actual_type: VariantType,
        message: String,
    },
}

impl fmt::Display for EncodeErrorKind {
    fn fmt(&self, output: &mut fmt::Formatter) -> fmt::Result {
        use self::EncodeErrorKind::*;

        match self {
            Io(err) => write!(output, "{}", err),
            Xml(err) => write!(output, "{}", err),

            UnknownProperty {
                class_name,
                property_name,
            } => write!(
                output,
                "Property {}.{} is unknown",
                class_name, property_name
            ),
            UnsupportedPropertyType(ty) => {
                write!(output, "Properties of type {:?} cannot be encoded yet", ty)
            }
            UnsupportedPropertyConversion {
                class_name,
                property_name,
                expected_type,
                actual_type,
                message,
            } => write!(
                output,
                "Property {}.{} is expected to be of type {:?}, but it was of type {:?} \
                 When trying to convert the value, this error occured: {}",
                class_name, property_name, expected_type, actual_type, message
            ),
        }
    }
}

impl std::error::Error for EncodeErrorKind {
    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
        use self::EncodeErrorKind::*;

        match self {
            Io(err) => Some(err),
            Xml(err) => Some(err),

            UnknownProperty { .. }
            | UnsupportedPropertyType(_)
            | UnsupportedPropertyConversion { .. } => None,
        }
    }
}

impl From<xml::writer::Error> for EncodeErrorKind {
    fn from(error: xml::writer::Error) -> EncodeErrorKind {
        EncodeErrorKind::Xml(error)
    }
}

impl From<io::Error> for EncodeErrorKind {
    fn from(error: io::Error) -> EncodeErrorKind {
        EncodeErrorKind::Io(error)
    }
}