//! Semantic Tokens helpers

use std::ops;

use lsp_types::{
    Range, SemanticToken, SemanticTokenModifier, SemanticTokenType, SemanticTokens,
    SemanticTokensEdit,
};

macro_rules! define_semantic_token_types {
    ($(($ident:ident, $string:literal)),*$(,)?) => {
        $(pub(crate) const $ident: SemanticTokenType = SemanticTokenType::new($string);)*

        pub(crate) const SUPPORTED_TYPES: &[SemanticTokenType] = &[
            SemanticTokenType::COMMENT,
            SemanticTokenType::KEYWORD,
            SemanticTokenType::STRING,
            SemanticTokenType::NUMBER,
            SemanticTokenType::REGEXP,
            SemanticTokenType::OPERATOR,
            SemanticTokenType::NAMESPACE,
            SemanticTokenType::TYPE,
            SemanticTokenType::STRUCT,
            SemanticTokenType::CLASS,
            SemanticTokenType::INTERFACE,
            SemanticTokenType::ENUM,
            SemanticTokenType::TYPE_PARAMETER,
            SemanticTokenType::FUNCTION,
            SemanticTokenType::MEMBER,
            SemanticTokenType::PROPERTY,
            SemanticTokenType::MACRO,
            SemanticTokenType::VARIABLE,
            SemanticTokenType::PARAMETER,
            SemanticTokenType::LABEL,
            $($ident),*
        ];
    };
}

define_semantic_token_types![
    (ATTRIBUTE, "attribute"),
    (BOOLEAN, "boolean"),
    (BUILTIN_TYPE, "builtinType"),
    (ENUM_MEMBER, "enumMember"),
    (ESCAPE_SEQUENCE, "escapeSequence"),
    (FORMAT_SPECIFIER, "formatSpecifier"),
    (GENERIC, "generic"),
    (LIFETIME, "lifetime"),
    (PUNCTUATION, "punctuation"),
    (SELF_KEYWORD, "selfKeyword"),
    (TYPE_ALIAS, "typeAlias"),
    (UNION, "union"),
    (UNRESOLVED_REFERENCE, "unresolvedReference"),
];

macro_rules! define_semantic_token_modifiers {
    ($(($ident:ident, $string:literal)),*$(,)?) => {
        $(pub(crate) const $ident: SemanticTokenModifier = SemanticTokenModifier::new($string);)*

        pub(crate) const SUPPORTED_MODIFIERS: &[SemanticTokenModifier] = &[
            SemanticTokenModifier::DOCUMENTATION,
            SemanticTokenModifier::DECLARATION,
            SemanticTokenModifier::DEFINITION,
            SemanticTokenModifier::STATIC,
            SemanticTokenModifier::ABSTRACT,
            SemanticTokenModifier::DEPRECATED,
            SemanticTokenModifier::READONLY,
            $($ident),*
        ];
    };
}

define_semantic_token_modifiers![
    (CONSTANT, "constant"),
    (CONTROL_FLOW, "controlFlow"),
    (INJECTED, "injected"),
    (MUTABLE, "mutable"),
    (UNSAFE, "unsafe"),
    (ATTRIBUTE_MODIFIER, "attribute"),
];

#[derive(Default)]
pub(crate) struct ModifierSet(pub(crate) u32);

impl ops::BitOrAssign<SemanticTokenModifier> for ModifierSet {
    fn bitor_assign(&mut self, rhs: SemanticTokenModifier) {
        let idx = SUPPORTED_MODIFIERS.iter().position(|it| it == &rhs).unwrap();
        self.0 |= 1 << idx;
    }
}

/// Tokens are encoded relative to each other.
///
/// This is a direct port of https://github.com/microsoft/vscode-languageserver-node/blob/f425af9de46a0187adb78ec8a46b9b2ce80c5412/server/src/sematicTokens.proposed.ts#L45
pub(crate) struct SemanticTokensBuilder {
    id: String,
    prev_line: u32,
    prev_char: u32,
    data: Vec<SemanticToken>,
}

impl SemanticTokensBuilder {
    pub fn new(id: String) -> Self {
        SemanticTokensBuilder { id, prev_line: 0, prev_char: 0, data: Default::default() }
    }

    /// Push a new token onto the builder
    pub fn push(&mut self, range: Range, token_index: u32, modifier_bitset: u32) {
        let mut push_line = range.start.line as u32;
        let mut push_char = range.start.character as u32;

        if !self.data.is_empty() {
            push_line -= self.prev_line;
            if push_line == 0 {
                push_char -= self.prev_char;
            }
        }

        // A token cannot be multiline
        let token_len = range.end.character - range.start.character;

        let token = SemanticToken {
            delta_line: push_line,
            delta_start: push_char,
            length: token_len as u32,
            token_type: token_index,
            token_modifiers_bitset: modifier_bitset,
        };

        self.data.push(token);

        self.prev_line = range.start.line as u32;
        self.prev_char = range.start.character as u32;
    }

    pub fn build(self) -> SemanticTokens {
        SemanticTokens { result_id: Some(self.id), data: self.data }
    }
}

pub fn diff_tokens(old: &[SemanticToken], new: &[SemanticToken]) -> Vec<SemanticTokensEdit> {
    let offset = new.iter().zip(old.iter()).take_while(|&(n, p)| n == p).count();

    let (_, old) = old.split_at(offset);
    let (_, new) = new.split_at(offset);

    let offset_from_end =
        new.iter().rev().zip(old.iter().rev()).take_while(|&(n, p)| n == p).count();

    let (old, _) = old.split_at(old.len() - offset_from_end);
    let (new, _) = new.split_at(new.len() - offset_from_end);

    if old.is_empty() && new.is_empty() {
        vec![]
    } else {
        // The lsp data field is actually a byte-diff but we
        // travel in tokens so `start` and `delete_count` are in multiples of the
        // serialized size of `SemanticToken`.
        vec![SemanticTokensEdit {
            start: 5 * offset as u32,
            delete_count: 5 * old.len() as u32,
            data: Some(new.into()),
        }]
    }
}

pub fn type_index(type_: SemanticTokenType) -> u32 {
    SUPPORTED_TYPES.iter().position(|it| *it == type_).unwrap() as u32
}

#[cfg(test)]
mod tests {
    use super::*;

    fn from(t: (u32, u32, u32, u32, u32)) -> SemanticToken {
        SemanticToken {
            delta_line: t.0,
            delta_start: t.1,
            length: t.2,
            token_type: t.3,
            token_modifiers_bitset: t.4,
        }
    }

    #[test]
    fn test_diff_insert_at_end() {
        let before = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];
        let after = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10)), from((11, 12, 13, 14, 15))];

        let edits = diff_tokens(&before, &after);
        assert_eq!(
            edits[0],
            SemanticTokensEdit {
                start: 10,
                delete_count: 0,
                data: Some(vec![from((11, 12, 13, 14, 15))])
            }
        );
    }

    #[test]
    fn test_diff_insert_at_beginning() {
        let before = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];
        let after = [from((11, 12, 13, 14, 15)), from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];

        let edits = diff_tokens(&before, &after);
        assert_eq!(
            edits[0],
            SemanticTokensEdit {
                start: 0,
                delete_count: 0,
                data: Some(vec![from((11, 12, 13, 14, 15))])
            }
        );
    }

    #[test]
    fn test_diff_insert_in_middle() {
        let before = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];
        let after = [
            from((1, 2, 3, 4, 5)),
            from((10, 20, 30, 40, 50)),
            from((60, 70, 80, 90, 100)),
            from((6, 7, 8, 9, 10)),
        ];

        let edits = diff_tokens(&before, &after);
        assert_eq!(
            edits[0],
            SemanticTokensEdit {
                start: 5,
                delete_count: 0,
                data: Some(vec![from((10, 20, 30, 40, 50)), from((60, 70, 80, 90, 100))])
            }
        );
    }

    #[test]
    fn test_diff_remove_from_end() {
        let before = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10)), from((11, 12, 13, 14, 15))];
        let after = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];

        let edits = diff_tokens(&before, &after);
        assert_eq!(edits[0], SemanticTokensEdit { start: 10, delete_count: 5, data: Some(vec![]) });
    }

    #[test]
    fn test_diff_remove_from_beginning() {
        let before = [from((11, 12, 13, 14, 15)), from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];
        let after = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];

        let edits = diff_tokens(&before, &after);
        assert_eq!(edits[0], SemanticTokensEdit { start: 0, delete_count: 5, data: Some(vec![]) });
    }

    #[test]
    fn test_diff_remove_from_middle() {
        let before = [
            from((1, 2, 3, 4, 5)),
            from((10, 20, 30, 40, 50)),
            from((60, 70, 80, 90, 100)),
            from((6, 7, 8, 9, 10)),
        ];
        let after = [from((1, 2, 3, 4, 5)), from((6, 7, 8, 9, 10))];

        let edits = diff_tokens(&before, &after);
        assert_eq!(edits[0], SemanticTokensEdit { start: 5, delete_count: 10, data: Some(vec![]) });
    }
}
