/*! The sixtyfps language parser

This module is responsible to parse a string onto a syntax tree.

The core of it is the `DefaultParser` class that holds a list of token and
generates a `rowan::GreenNode`

This module has different sub modules with the actual parser functions

*/

use crate::diagnostics::Diagnostics;
pub use rowan::SmolStr;
use std::convert::TryFrom;

mod document;
mod expressions;
mod statements;

/// Each parser submodule would simply do `use super::prelude::*` to import typically used items
mod prelude {
    #[cfg(test)]
    pub use super::{syntax_nodes, SyntaxNode, SyntaxNodeVerify};
    pub use super::{DefaultParser, Parser, SyntaxKind};
    #[cfg(test)]
    pub use parser_test_macro::parser_test;
}

#[cfg(test)]
pub trait SyntaxNodeVerify {
    /// The SyntaxKind corresponding to this type
    const KIND: SyntaxKind;
    /// Asserts that the node is of the given SyntaxKind and that it has the expected children
    /// Panic if this is not the case
    fn verify(node: SyntaxNode) {
        assert_eq!(node.kind(), Self::KIND)
    }
}

/// Check that a node has the assumed children
#[cfg(test)]
macro_rules! verify_node {
    // nothing to verify
    ($node:ident, _) => {};
    // Some combination of children
    ($node:ident, [ $($t1:tt $($t2:ident)?),* ]) => {
        // Check that every children is there
        $(verify_node!(@check_has_children $node, $t1 $($t2)* );)*

        // check that there are not too many nodes
        for c in $node.children() {
            assert!(
                false $(|| c.kind() == verify_node!(@extract_kind $t1 $($t2)*))*,
                format!("Node is none of [{}]\n{:?}", stringify!($($t1 $($t2)*),*) ,c));
        }

        // recurse
        $(
            for _c in $node.children().filter(|n| n.kind() == verify_node!(@extract_kind $t1 $($t2)*)) {
                <verify_node!(@extract_type $t1 $($t2)*)>::verify(_c)
            }
        )*
    };

    // Any number of this kind.
    (@check_has_children $node:ident, * $kind:ident) => {};
    // 1 or 0
    (@check_has_children $node:ident, ? $kind:ident) => {
        let count = $node.children_with_tokens().filter(|n| n.kind() == SyntaxKind::$kind).count();
        assert!(count <= 1, "Expecting one or zero sub-node of type {}, found {}\n{:?}", stringify!($kind), count, $node);
    };
    // Exactly one
    (@check_has_children $node:ident, $kind:ident) => {
        let count = $node.children_with_tokens().filter(|n| n.kind() == SyntaxKind::$kind).count();
        assert_eq!(count, 1, "Expecting exactly one sub-node of type {}\n{:?}", stringify!($kind), $node);
    };
    // Exact number
    (@check_has_children $node:ident, $count:literal $kind:ident) => {
        let count = $node.children_with_tokens().filter(|n| n.kind() == SyntaxKind::$kind).count();
        assert_eq!(count, $count, "Expecting {} sub-node of type {}, found {}\n{:?}", $count, stringify!($kind), count, $node);
    };

    (@extract_kind * $kind:ident) => {SyntaxKind::$kind};
    (@extract_kind ? $kind:ident) => {SyntaxKind::$kind};
    (@extract_kind $count:literal $kind:ident) => {SyntaxKind::$kind};
    (@extract_kind $kind:ident) => {SyntaxKind::$kind};

    (@extract_type * $kind:ident) => {$crate::parser::syntax_nodes::$kind};
    (@extract_type ? $kind:ident) => {$crate::parser::syntax_nodes::$kind};
    (@extract_type $count:literal $kind:ident) => {$crate::parser::syntax_nodes::$kind};
    (@extract_type $kind:ident) => {$crate::parser::syntax_nodes::$kind};
}

macro_rules! node_accessors {
    // nothing
    (_) => {};
    // Some combination of children
    ([ $($t1:tt $($t2:ident)?),* ]) => {
        $(node_accessors!{@ $t1 $($t2)*} )*
    };

    (@ * $kind:ident) => {
        #[allow(non_snake_case)]
        pub fn $kind(&self) -> impl Iterator<Item = $kind> {
            self.0.children().filter(|n| n.kind() ==SyntaxKind::$kind).map(Into::into)
        }
    };
    (@ ? $kind:ident) => {
        #[allow(non_snake_case)]
        pub fn $kind(&self) -> Option<$kind> {
            self.0.child_node(SyntaxKind::$kind).map(Into::into)
        }
    };
    (@ 2 $kind:ident) => {
        #[allow(non_snake_case)]
        pub fn $kind(&self) -> ($kind, $kind) {
            let mut it = self.0.children().filter(|n| n.kind() == SyntaxKind::$kind);
            let a = it.next().unwrap();
            let b = it.next().unwrap();
            debug_assert!(it.next().is_none());
            (a.into(), b.into())
        }
    };
    (@ 3 $kind:ident) => {
        #[allow(non_snake_case)]
        pub fn $kind(&self) -> ($kind, $kind, $kind) {
            let mut it = self.0.children().filter(|n| n.kind() == SyntaxKind::$kind);
            let a = it.next().unwrap();
            let b = it.next().unwrap();
            let c = it.next().unwrap();
            debug_assert!(it.next().is_none());
            (a.into(), b.into(), c.into())
        }
    };
    (@ $kind:ident) => {
        #[allow(non_snake_case)]
        pub fn $kind(&self) -> $kind {
            self.0.child_node(SyntaxKind::$kind).unwrap().into()
        }
    };

}

/// This macro is invoked once, to declare all the token and syntax kind.
/// The purpose of this macro is to declare the token with its regexp at the same place,
/// and the nodes with their contents.
macro_rules! declare_syntax {
    ({
        $($token:ident -> $rx:expr ,)*
     }
     {
        $( $(#[$attr:meta])*  $nodekind:ident -> $children:tt ,)*
    })
    => {
        #[repr(u16)]
        #[derive(Debug, Copy, Clone, Eq, PartialEq, num_enum::IntoPrimitive, num_enum::TryFromPrimitive)]
        pub enum SyntaxKind {
            Error,
            Eof,

            // Tokens:
            $(
                /// Token matching this regexp:
                /// ```text
                #[doc = $rx]
                /// ```
                $token,
            )*

            // Nodes:
            $(
                $(#[$attr])*
                $nodekind,
            )*
        }

        fn lexer() -> m_lexer::Lexer {
            m_lexer::LexerBuilder::new()
                .error_token(m_lexer::TokenKind(SyntaxKind::Error.into()))
                .tokens(&[
                    $((m_lexer::TokenKind(SyntaxKind::$token.into()), $rx)),*
                ])
                .build()
        }

        pub mod syntax_nodes {
            use super::*;
            use derive_more::*;
            $(
                #[derive(Debug, Clone, From, Deref, DerefMut, Into)]
                pub struct $nodekind(pub SyntaxNode);
                #[cfg(test)]
                impl SyntaxNodeVerify for $nodekind {
                    const KIND: SyntaxKind = SyntaxKind::$nodekind;
                    fn verify(node: SyntaxNode) {
                        assert_eq!(node.kind(), Self::KIND);
                        verify_node!(node, $children);
                    }
                }
                impl $nodekind {
                    node_accessors!{$children}
                }
            )*
        }
    }
}
declare_syntax! {
    // Tokens.
    // WARNING: when changing this, do not forget to update the tokenizer in the sixtyfps-rs-macro crate!
    {
        Whitespace -> r"\s+",
        Comment -> r"//.*\n|(?sU)/\*.*\*/", // FIXME: comments within comments
        StringLiteral -> r#""[^"]*""#, // FIXME: escapes
        NumberLiteral -> r"[\d]+(\.[\d]*)?",
        ColorLiteral -> r"#[\w]+",
        Identifier -> r"[\w]+",
        LBrace -> r"\{",
        RBrace -> r"\}",
        LParent -> r"\(",
        RParent -> r"\)",
        LAngle -> r"<",
        RAngle -> r">",
        LBracket -> r"\[",
        RBracket -> r"\]",
        Plus -> r"\+",
        Minus -> r"-",
        Star -> r"\*",
        Div -> r"/",
        PlusEqual -> r"\+=",
        MinusEqual -> r"-=",
        StarEqual -> r"\*=",
        DivEqual -> r"/=",
        ColonEqual -> r":=",
        FatArrow -> r"=>",
        Equal -> r"=",
        Colon -> r":",
        Comma -> r",",
        Semicolon -> r";",
        Bang -> r"!",
        Dot -> r"\.",
        Question -> r"\?",
    }
    // syntax kind
    {
        Document -> [ *Component ],
        Component -> [ Element ],
        /// Note: This is in fact the same as Component as far as the parser is concerned
        SubElement -> [ Element ],
        Element -> [ QualifiedName, *PropertyDeclaration, *Binding, *SignalConnection, *SignalDeclaration, *SubElement, *RepeatedElement ],
        RepeatedElement -> [ ?DeclaredIdentifier, ?RepeatedIndex, Expression , Element],
        RepeatedIndex -> [],
        SignalDeclaration -> [ DeclaredIdentifier ],
        SignalConnection -> [ CodeBlock ],
        PropertyDeclaration-> [ QualifiedName , DeclaredIdentifier, ?BindingExpression ],
        /// wraps Identifiers, like `Rectangle` or `SomeModule.SomeType`
        QualifiedName-> [],
        /// Wraps single identifier (to disambiguate when there are other identifiar in the production)
        DeclaredIdentifier -> [],
        Binding-> [ BindingExpression ],
        /// the right-hand-side of a binding
        // Fixme: the test should be a or
        BindingExpression-> [ ?CodeBlock, ?Expression ],
        CodeBlock-> [ *Expression ],
        // FIXME: the test should test that as alternative rather than several of them (but it can also be a literal)
        Expression-> [ ?Expression, ?BangExpression, ?FunctionCallExpression, ?SelfAssignment,
                       ?ConditionalExpression, ?QualifiedName, ?BinaryExpression, ?Array, ?ObjectLiteral],
        /// `foo!bar`
        BangExpression -> [Expression],
        /// expression()
        FunctionCallExpression -> [Expression],
        /// `expression += expression`
        SelfAssignment -> [2 Expression],
        /// `condition ? first : second`
        ConditionalExpression -> [3 Expression],
        /// `expr + expr`
        BinaryExpression -> [2 Expression],
        /// `[ ... ]`
        Array -> [ *Expression ],
        /// `{ foo: bar }`
        ObjectLiteral -> [ *ObjectMember ],
        /// `foo: bar` inside an ObjectLiteral
        ObjectMember -> [ Expression ],
    }
}

impl From<SyntaxKind> for rowan::SyntaxKind {
    fn from(v: SyntaxKind) -> Self {
        rowan::SyntaxKind(v.into())
    }
}

#[derive(Clone, Debug)]
pub struct Token {
    pub kind: SyntaxKind,
    pub text: SmolStr,
    pub offset: usize,
    #[cfg(feature = "proc_macro_span")]
    pub span: Option<proc_macro::Span>,
}

impl Default for Token {
    fn default() -> Self {
        Token {
            kind: SyntaxKind::Eof,
            text: Default::default(),
            offset: 0,
            #[cfg(feature = "proc_macro_span")]
            span: None,
        }
    }
}

impl Token {
    pub fn as_str(&self) -> &str {
        self.text.as_str()
    }
}

mod parser_trait {
    //! module allowing to keep implementation details of the node private
    use super::*;

    pub trait Parser: Sized {
        type Checkpoint: Clone;

        /// Enter a new node.  The node is going to be finished when
        /// The return value of this function is drop'ed
        ///
        /// (do not re-implement this function, re-implement
        /// start_node_impl and finish_node_impl)
        #[must_use = "The node will be finished when it is dropped"]
        fn start_node(&mut self, kind: SyntaxKind) -> Node<Self> {
            self.start_node_impl(kind, None, NodeToken(()));
            Node(self)
        }
        #[must_use = "use start_node_at to use this checkpoint"]
        fn checkpoint(&mut self) -> Self::Checkpoint;
        #[must_use = "The node will be finished when it is dropped"]
        fn start_node_at(&mut self, checkpoint: Self::Checkpoint, kind: SyntaxKind) -> Node<Self> {
            self.start_node_impl(kind, Some(checkpoint), NodeToken(()));
            Node(self)
        }

        /// Can only be called by Node::drop
        fn finish_node_impl(&mut self, token: NodeToken);
        /// Can only be called by Self::start_node
        fn start_node_impl(
            &mut self,
            kind: SyntaxKind,
            checkpoint: Option<Self::Checkpoint>,
            token: NodeToken,
        );
        fn peek(&mut self) -> Token;
        /// Peek the n'th token, not including whitespaces and comments
        fn nth(&mut self, n: usize) -> SyntaxKind;
        fn consume(&mut self);
        fn error(&mut self, e: impl Into<String>);

        /// Consume the token if it has the right kind, otherwise report a syntax error.
        /// Returns true if the token was consumed.
        fn expect(&mut self, kind: SyntaxKind) -> bool {
            if !self.test(kind) {
                self.error(format!("Syntax error: expected {:?}", kind));
                return false;
            }
            return true;
        }

        /// If the token if of this type, consume it and return true, otherwise return false
        fn test(&mut self, kind: SyntaxKind) -> bool {
            if self.nth(0) != kind {
                return false;
            }
            self.consume();
            return true;
        }

        /// consume everyting until reaching a token of this kind
        fn until(&mut self, kind: SyntaxKind) {
            // FIXME! match {} () []
            while {
                let k = self.nth(0);
                k != kind && k != SyntaxKind::Eof
            } {
                self.consume();
            }
            self.expect(kind);
        }
    }

    /// A token to proof that start_node_impl and finish_node_impl are only
    /// called from the Node implementation
    ///
    /// Since the constructor is private, it cannot be produced by anything else.
    pub struct NodeToken(());
    /// The return value of `DefaultParser::start_node`. This borrows the parser
    /// and finishes the node on Drop
    #[derive(derive_more::DerefMut)]
    pub struct Node<'a, P: Parser>(&'a mut P);
    impl<'a, P: Parser> Drop for Node<'a, P> {
        fn drop(&mut self) {
            self.0.finish_node_impl(NodeToken(()));
        }
    }
    impl<'a, P: Parser> core::ops::Deref for Node<'a, P> {
        type Target = P;
        fn deref(&self) -> &Self::Target {
            self.0
        }
    }
}
#[doc(inline)]
pub use parser_trait::*;

pub struct DefaultParser {
    builder: rowan::GreenNodeBuilder<'static>,
    tokens: Vec<Token>,
    cursor: usize,
    diags: Diagnostics,
}

impl From<Vec<Token>> for DefaultParser {
    fn from(tokens: Vec<Token>) -> Self {
        Self { builder: Default::default(), tokens, cursor: 0, diags: Default::default() }
    }
}

impl DefaultParser {
    /// Constructor that create a parser from the source code
    pub fn new(source: &str) -> Self {
        fn lex(source: &str) -> Vec<Token> {
            lexer()
                .tokenize(source)
                .into_iter()
                .scan(0usize, |start_offset, t| {
                    let s: rowan::SmolStr = source[*start_offset..*start_offset + t.len].into();
                    let offset = *start_offset;
                    *start_offset += t.len;
                    Some(Token {
                        kind: SyntaxKind::try_from(t.kind.0).unwrap(),
                        text: s,
                        offset,
                        ..Default::default()
                    })
                })
                .collect()
        }
        Self::from(lex(source))
    }

    fn current_token(&self) -> Token {
        self.tokens.get(self.cursor).cloned().unwrap_or_default()
    }

    /// Consume all the whitespace
    pub fn consume_ws(&mut self) {
        while matches!(self.current_token().kind, SyntaxKind::Whitespace | SyntaxKind::Comment) {
            self.consume()
        }
    }
}

impl Parser for DefaultParser {
    fn start_node_impl(
        &mut self,
        kind: SyntaxKind,
        checkpoint: Option<Self::Checkpoint>,
        _: NodeToken,
    ) {
        match checkpoint {
            None => self.builder.start_node(kind.into()),
            Some(cp) => self.builder.start_node_at(cp, kind.into()),
        }
    }

    fn finish_node_impl(&mut self, _: NodeToken) {
        self.builder.finish_node();
    }

    fn peek(&mut self) -> Token {
        self.consume_ws();
        self.current_token()
    }

    /// Peek the n'th token, not including whitespaces and comments
    fn nth(&mut self, mut n: usize) -> SyntaxKind {
        self.consume_ws();
        let mut c = self.cursor;
        while n > 0 {
            n -= 1;
            c += 1;
            while c < self.tokens.len()
                && matches!(self.tokens[c].kind, SyntaxKind::Whitespace | SyntaxKind::Comment)
            {
                c += 1;
            }
        }
        self.tokens.get(c).map_or(SyntaxKind::Eof, |x| x.kind)
    }

    /// Consume the current token
    fn consume(&mut self) {
        let t = self.current_token();
        self.builder.token(t.kind.into(), t.text);
        self.cursor += 1;
    }

    /// Reports an error at the current token location
    fn error(&mut self, e: impl Into<String>) {
        let current_token = self.current_token();
        #[allow(unused_mut)]
        let mut span = crate::diagnostics::Span::new(current_token.offset);
        #[cfg(feature = "proc_macro_span")]
        {
            span.span = current_token.span;
        }
        self.diags.push_error(e.into(), span);
    }

    type Checkpoint = rowan::Checkpoint;
    fn checkpoint(&mut self) -> Self::Checkpoint {
        self.builder.checkpoint()
    }
}

#[derive(Clone, Copy, Debug, Eq, Ord, Hash, PartialEq, PartialOrd)]
pub enum Language {}
impl rowan::Language for Language {
    type Kind = SyntaxKind;
    fn kind_from_raw(raw: rowan::SyntaxKind) -> Self::Kind {
        SyntaxKind::try_from(raw.0).unwrap()
    }
    fn kind_to_raw(kind: Self::Kind) -> rowan::SyntaxKind {
        kind.into()
    }
}

pub type SyntaxNode = rowan::SyntaxNode<Language>;
pub type SyntaxToken = rowan::SyntaxToken<Language>;

/// Helper functions to easily get the children of a given kind.
/// This traits is only supposed to be implemented on SyntaxNope
pub trait SyntaxNodeEx {
    fn child_node(&self, kind: SyntaxKind) -> Option<SyntaxNode>;
    fn child_token(&self, kind: SyntaxKind) -> Option<SyntaxToken>;
    fn child_text(&self, kind: SyntaxKind) -> Option<String>;
}

impl SyntaxNodeEx for SyntaxNode {
    fn child_node(&self, kind: SyntaxKind) -> Option<SyntaxNode> {
        self.children().find(|n| n.kind() == kind)
    }
    fn child_token(&self, kind: SyntaxKind) -> Option<SyntaxToken> {
        self.children_with_tokens().find(|n| n.kind() == kind).and_then(|x| x.into_token())
    }
    fn child_text(&self, kind: SyntaxKind) -> Option<String> {
        self.children_with_tokens()
            .find(|n| n.kind() == kind)
            .and_then(|x| x.as_token().map(|x| x.text().to_string()))
    }
}

/// Returns a span.  This is implemented for tokens and nodes
pub trait Spanned {
    fn span(&self) -> crate::diagnostics::Span;
}

impl Spanned for SyntaxNode {
    fn span(&self) -> crate::diagnostics::Span {
        crate::diagnostics::Span::new(self.text_range().start().into())
    }
}

impl Spanned for SyntaxToken {
    fn span(&self) -> crate::diagnostics::Span {
        crate::diagnostics::Span::new(self.text_range().start().into())
    }
}

// Actual parser
pub fn parse(source: &str) -> (SyntaxNode, Diagnostics) {
    let mut p = DefaultParser::new(source);
    document::parse_document(&mut p);
    (SyntaxNode::new_root(p.builder.finish()), p.diags)
}

#[allow(dead_code)]
pub fn parse_tokens(tokens: Vec<Token>) -> (SyntaxNode, Diagnostics) {
    let mut p = DefaultParser::from(tokens);
    document::parse_document(&mut p);
    (SyntaxNode::new_root(p.builder.finish()), p.diags)
}