//! Implements syntax highlighting.

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

use hir::{Name, Semantics};
use ra_ide_db::{
    defs::{classify_name, classify_name_ref, Definition, NameClass, NameRefClass},
    RootDatabase,
};
use ra_prof::profile;
use ra_syntax::{
    ast::{self, HasQuotes, HasStringValue},
    AstNode, AstToken, Direction, NodeOrToken, SyntaxElement,
    SyntaxKind::*,
    SyntaxToken, TextRange, WalkEvent, T,
};
use rustc_hash::FxHashMap;

use crate::{call_info::ActiveParameter, Analysis, FileId};

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

#[derive(Debug, Clone)]
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();
    // We use a stack for the DFS traversal below.
    // When we leave a node, the we use it to flatten the highlighted ranges.
    let mut res: Vec<Vec<HighlightedRange>> = vec![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() {
        match &event {
            WalkEvent::Enter(_) => res.push(Vec::new()),
            WalkEvent::Leave(_) => {
                /* Flattens the highlighted ranges.
                 *
                 * For example `#[cfg(feature = "foo")]` contains the nested ranges:
                 * 1) parent-range: Attribute [0, 23)
                 * 2) child-range: String [16, 21)
                 *
                 * The following code implements the flattening, for our example this results to:
                 * `[Attribute [0, 16), String [16, 21), Attribute [21, 23)]`
                 */
                let children = res.pop().unwrap();
                let prev = res.last_mut().unwrap();
                let needs_flattening = !children.is_empty()
                    && !prev.is_empty()
                    && children.first().unwrap().range.is_subrange(&prev.last().unwrap().range);
                if !needs_flattening {
                    prev.extend(children);
                } else {
                    let mut parent = prev.pop().unwrap();
                    for ele in children {
                        assert!(ele.range.is_subrange(&parent.range));
                        let mut cloned = parent.clone();
                        parent.range = TextRange::from_to(parent.range.start(), ele.range.start());
                        cloned.range = TextRange::from_to(ele.range.end(), cloned.range.end());
                        if !parent.range.is_empty() {
                            prev.push(parent);
                        }
                        prev.push(ele);
                        parent = cloned;
                    }
                    if !parent.range.is_empty() {
                        prev.push(parent);
                    }
                }
            }
        };
        let current = res.last_mut().expect("during DFS traversal, the stack must not be empty");

        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) {
                    current.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.clone().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.clone()
        };

        if let Some(token) = element.as_token().cloned().and_then(ast::RawString::cast) {
            let expanded = element_to_highlight.as_token().unwrap().clone();
            if highlight_injection(current, &sema, token, expanded).is_some() {
                continue;
            }
        }

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

    assert_eq!(res.len(), 1, "after DFS traversal, the stack should only contain a single element");
    let mut res = res.pop().unwrap();
    res.sort_by_key(|range| range.range.start());
    // Check that ranges are sorted and disjoint
    assert!(res
        .iter()
        .zip(res.iter().skip(1))
        .all(|(left, right)| left.range.end() <= right.range.start()));
    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(NameClass::Definition(Definition::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(NameClass::Definition(def)) => {
                    highlight_name(db, def) | HighlightModifier::Definition
                }
                Some(NameClass::ConstReference(def)) => highlight_name(db, def),
                None => highlight_name_by_syntax(name) | HighlightModifier::Definition,
            }
        }

        // Highlight references like the definitions they resolve to
        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();
            match classify_name_ref(sema, &name_ref) {
                Some(name_kind) => match name_kind {
                    NameRefClass::Definition(def) => {
                        if let Definition::Local(local) = &def {
                            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, def)
                    }
                    NameRefClass::FieldShorthand { .. } => HighlightTag::Field.into(),
                },
                None => HighlightTag::UnresolvedReference.into(),
            }
        }

        // Simple token-based highlighting
        COMMENT => HighlightTag::Comment.into(),
        STRING | RAW_STRING | RAW_BYTE_STRING | BYTE_STRING => HighlightTag::StringLiteral.into(),
        ATTR => HighlightTag::Attribute.into(),
        INT_NUMBER | FLOAT_NUMBER => HighlightTag::NumericLiteral.into(),
        BYTE => HighlightTag::ByteLiteral.into(),
        CHAR => HighlightTag::CharLiteral.into(),
        LIFETIME => {
            let h = Highlight::new(HighlightTag::Lifetime);
            match element.parent().map(|it| it.kind()) {
                Some(LIFETIME_PARAM) | Some(LABEL) => h | HighlightModifier::Definition,
                _ => h,
            }
        }

        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::ControlFlow,
                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: Definition) -> Highlight {
    match def {
        Definition::Macro(_) => HighlightTag::Macro,
        Definition::StructField(_) => HighlightTag::Field,
        Definition::ModuleDef(def) => match def {
            hir::ModuleDef::Module(_) => HighlightTag::Module,
            hir::ModuleDef::Function(_) => HighlightTag::Function,
            hir::ModuleDef::Adt(hir::Adt::Struct(_)) => HighlightTag::Struct,
            hir::ModuleDef::Adt(hir::Adt::Enum(_)) => HighlightTag::Enum,
            hir::ModuleDef::Adt(hir::Adt::Union(_)) => HighlightTag::Union,
            hir::ModuleDef::EnumVariant(_) => HighlightTag::EnumVariant,
            hir::ModuleDef::Const(_) => HighlightTag::Constant,
            hir::ModuleDef::Static(_) => HighlightTag::Static,
            hir::ModuleDef::Trait(_) => HighlightTag::Trait,
            hir::ModuleDef::TypeAlias(_) => HighlightTag::TypeAlias,
            hir::ModuleDef::BuiltinType(_) => HighlightTag::BuiltinType,
        },
        Definition::SelfType(_) => HighlightTag::SelfType,
        Definition::TypeParam(_) => HighlightTag::TypeParam,
        // FIXME: distinguish between locals and parameters
        Definition::Local(local) => {
            let mut h = Highlight::new(HighlightTag::Local);
            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 => HighlightTag::Struct.into(),
        ENUM_DEF => HighlightTag::Enum.into(),
        UNION_DEF => HighlightTag::Union.into(),
        TRAIT_DEF => HighlightTag::Trait.into(),
        TYPE_ALIAS_DEF => HighlightTag::TypeAlias.into(),
        TYPE_PARAM => HighlightTag::TypeParam.into(),
        RECORD_FIELD_DEF => HighlightTag::Field.into(),
        _ => default,
    }
}

fn highlight_injection(
    acc: &mut Vec<HighlightedRange>,
    sema: &Semantics<RootDatabase>,
    literal: ast::RawString,
    expanded: SyntaxToken,
) -> Option<()> {
    let active_parameter = ActiveParameter::at_token(&sema, expanded)?;
    if !active_parameter.name.starts_with("ra_fixture") {
        return None;
    }
    let value = literal.value()?;
    let (analysis, tmp_file_id) = Analysis::from_single_file(value);

    if let Some(range) = literal.open_quote_text_range() {
        acc.push(HighlightedRange {
            range,
            highlight: HighlightTag::StringLiteral.into(),
            binding_hash: None,
        })
    }

    for mut h in analysis.highlight(tmp_file_id).unwrap() {
        if let Some(r) = literal.map_range_up(h.range) {
            h.range = r;
            acc.push(h)
        }
    }

    if let Some(range) = literal.close_quote_text_range() {
        acc.push(HighlightedRange {
            range,
            highlight: HighlightTag::StringLiteral.into(),
            binding_hash: None,
        })
    }

    Some(())
}