//! Implements syntax highlighting.

mod tags;
mod html;
#[cfg(test)]
mod tests;

use hir::{Name, Semantics};
use ra_ide_db::{
    defs::{classify_name, NameDefinition},
    RootDatabase,
};
use ra_prof::profile;
use ra_syntax::{
    ast, AstNode, Direction, NodeOrToken, SyntaxElement, SyntaxKind::*, TextRange, WalkEvent, T,
};
use rustc_hash::FxHashMap;

use crate::{references::classify_name_ref, FileId};

pub(crate) use html::highlight_as_html;
pub use tags::{Highlight, HighlightModifier, HighlightModifiers, HighlightTag};

#[derive(Debug)]
pub struct HighlightedRange {
    pub range: TextRange,
    pub highlight: Highlight,
    pub binding_hash: Option<u64>,
}

pub(crate) fn highlight(
    db: &RootDatabase,
    file_id: FileId,
    range_to_highlight: Option<TextRange>,
) -> Vec<HighlightedRange> {
    let _p = profile("highlight");
    let sema = Semantics::new(db);

    // Determine the root based on the given range.
    let (root, range_to_highlight) = {
        let source_file = sema.parse(file_id);
        match range_to_highlight {
            Some(range) => {
                let node = match source_file.syntax().covering_element(range) {
                    NodeOrToken::Node(it) => it,
                    NodeOrToken::Token(it) => it.parent(),
                };
                (node, range)
            }
            None => (source_file.syntax().clone(), source_file.syntax().text_range()),
        }
    };

    let mut bindings_shadow_count: FxHashMap<Name, u32> = FxHashMap::default();
    let mut res = Vec::new();

    let mut current_macro_call: Option<ast::MacroCall> = None;

    // Walk all nodes, keeping track of whether we are inside a macro or not.
    // If in macro, expand it first and highlight the expanded code.
    for event in root.preorder_with_tokens() {
        let event_range = match &event {
            WalkEvent::Enter(it) => it.text_range(),
            WalkEvent::Leave(it) => it.text_range(),
        };

        // Element outside of the viewport, no need to highlight
        if range_to_highlight.intersection(&event_range).is_none() {
            continue;
        }

        // Track "inside macro" state
        match event.clone().map(|it| it.into_node().and_then(ast::MacroCall::cast)) {
            WalkEvent::Enter(Some(mc)) => {
                current_macro_call = Some(mc.clone());
                if let Some(range) = macro_call_range(&mc) {
                    res.push(HighlightedRange {
                        range,
                        highlight: HighlightTag::Macro.into(),
                        binding_hash: None,
                    });
                }
                continue;
            }
            WalkEvent::Leave(Some(mc)) => {
                assert!(current_macro_call == Some(mc));
                current_macro_call = None;
                continue;
            }
            _ => (),
        }

        let element = match event {
            WalkEvent::Enter(it) => it,
            WalkEvent::Leave(_) => continue,
        };
        let range = element.text_range();

        let element_to_highlight = if current_macro_call.is_some() {
            // Inside a macro -- expand it first
            let token = match element.into_token() {
                Some(it) if it.parent().kind() == TOKEN_TREE => it,
                _ => continue,
            };
            let token = sema.descend_into_macros(token.clone());
            let parent = token.parent();
            // We only care Name and Name_ref
            match (token.kind(), parent.kind()) {
                (IDENT, NAME) | (IDENT, NAME_REF) => parent.into(),
                _ => token.into(),
            }
        } else {
            element
        };

        if let Some((highlight, binding_hash)) =
            highlight_element(&sema, &mut bindings_shadow_count, element_to_highlight)
        {
            res.push(HighlightedRange { range, highlight, binding_hash });
        }
    }

    res
}

fn macro_call_range(macro_call: &ast::MacroCall) -> Option<TextRange> {
    let path = macro_call.path()?;
    let name_ref = path.segment()?.name_ref()?;

    let range_start = name_ref.syntax().text_range().start();
    let mut range_end = name_ref.syntax().text_range().end();
    for sibling in path.syntax().siblings_with_tokens(Direction::Next) {
        match sibling.kind() {
            T![!] | IDENT => range_end = sibling.text_range().end(),
            _ => (),
        }
    }

    Some(TextRange::from_to(range_start, range_end))
}

fn highlight_element(
    sema: &Semantics<RootDatabase>,
    bindings_shadow_count: &mut FxHashMap<Name, u32>,
    element: SyntaxElement,
) -> Option<(Highlight, Option<u64>)> {
    let db = sema.db;
    let mut binding_hash = None;
    let highlight: Highlight = match element.kind() {
        FN_DEF => {
            bindings_shadow_count.clear();
            return None;
        }

        // Highlight definitions depending on the "type" of the definition.
        NAME => {
            let name = element.into_node().and_then(ast::Name::cast).unwrap();
            let name_kind = classify_name(sema, &name);

            if let Some(NameDefinition::Local(local)) = &name_kind {
                if let Some(name) = local.name(db) {
                    let shadow_count = bindings_shadow_count.entry(name.clone()).or_default();
                    *shadow_count += 1;
                    binding_hash = Some(calc_binding_hash(&name, *shadow_count))
                }
            };

            match name_kind {
                Some(name_kind) => highlight_name(db, name_kind),
                None => highlight_name_by_syntax(name),
            }
        }

        // Highlight references like the definitions they resolve to

        // Special-case field init shorthand
        NAME_REF if element.parent().and_then(ast::RecordField::cast).is_some() => {
            HighlightTag::Field.into()
        }
        NAME_REF if element.ancestors().any(|it| it.kind() == ATTR) => return None,
        NAME_REF => {
            let name_ref = element.into_node().and_then(ast::NameRef::cast).unwrap();
            let name_kind = classify_name_ref(sema, &name_ref)?;

            if let NameDefinition::Local(local) = &name_kind {
                if let Some(name) = local.name(db) {
                    let shadow_count = bindings_shadow_count.entry(name.clone()).or_default();
                    binding_hash = Some(calc_binding_hash(&name, *shadow_count))
                }
            };

            highlight_name(db, name_kind)
        }

        // Simple token-based highlighting
        COMMENT => HighlightTag::Comment.into(),
        STRING | RAW_STRING | RAW_BYTE_STRING | BYTE_STRING => HighlightTag::LiteralString.into(),
        ATTR => HighlightTag::Attribute.into(),
        INT_NUMBER | FLOAT_NUMBER => HighlightTag::LiteralNumeric.into(),
        BYTE => HighlightTag::LiteralByte.into(),
        CHAR => HighlightTag::LiteralChar.into(),
        LIFETIME => HighlightTag::TypeLifetime.into(),

        k if k.is_keyword() => {
            let h = Highlight::new(HighlightTag::Keyword);
            match k {
                T![break]
                | T![continue]
                | T![else]
                | T![for]
                | T![if]
                | T![loop]
                | T![match]
                | T![return]
                | T![while] => h | HighlightModifier::Control,
                T![unsafe] => h | HighlightModifier::Unsafe,
                _ => h,
            }
        }

        _ => return None,
    };

    return Some((highlight, binding_hash));

    fn calc_binding_hash(name: &Name, shadow_count: u32) -> u64 {
        fn hash<T: std::hash::Hash + std::fmt::Debug>(x: T) -> u64 {
            use std::{collections::hash_map::DefaultHasher, hash::Hasher};

            let mut hasher = DefaultHasher::new();
            x.hash(&mut hasher);
            hasher.finish()
        }

        hash((name, shadow_count))
    }
}

fn highlight_name(db: &RootDatabase, def: NameDefinition) -> Highlight {
    match def {
        NameDefinition::Macro(_) => HighlightTag::Macro,
        NameDefinition::StructField(_) => HighlightTag::Field,
        NameDefinition::ModuleDef(def) => match def {
            hir::ModuleDef::Module(_) => HighlightTag::Module,
            hir::ModuleDef::Function(_) => HighlightTag::Function,
            hir::ModuleDef::Adt(_) => HighlightTag::Type,
            hir::ModuleDef::EnumVariant(_) => HighlightTag::Constant,
            hir::ModuleDef::Const(_) => HighlightTag::Constant,
            hir::ModuleDef::Static(_) => HighlightTag::Constant,
            hir::ModuleDef::Trait(_) => HighlightTag::Type,
            hir::ModuleDef::TypeAlias(_) => HighlightTag::Type,
            hir::ModuleDef::BuiltinType(_) => {
                return HighlightTag::Type | HighlightModifier::Builtin
            }
        },
        NameDefinition::SelfType(_) => HighlightTag::TypeSelf,
        NameDefinition::TypeParam(_) => HighlightTag::TypeParam,
        NameDefinition::Local(local) => {
            let mut h = Highlight::new(HighlightTag::Variable);
            if local.is_mut(db) || local.ty(db).is_mutable_reference() {
                h |= HighlightModifier::Mutable;
            }
            return h;
        }
    }
    .into()
}

fn highlight_name_by_syntax(name: ast::Name) -> Highlight {
    let default = HighlightTag::Function.into();

    let parent = match name.syntax().parent() {
        Some(it) => it,
        _ => return default,
    };

    match parent.kind() {
        STRUCT_DEF | ENUM_DEF | TRAIT_DEF | TYPE_ALIAS_DEF => HighlightTag::Type.into(),
        TYPE_PARAM => HighlightTag::TypeParam.into(),
        RECORD_FIELD_DEF => HighlightTag::Field.into(),
        _ => default,
    }
}