//! `ra_assists` crate provides a bunch of code assists, also known as code
//! actions (in LSP) or intentions (in IntelliJ).
//!
//! An assist is a micro-refactoring, which is automatically activated in
//! certain context. For example, if the cursor is over `,`, a "swap `,`" assist
//! becomes available.

mod assist_ctx;
mod marks;
#[cfg(test)]
mod doc_tests;
#[cfg(test)]
mod test_db;
pub mod ast_transform;

use either::Either;
use hir::{db::HirDatabase, InFile, ModPath, Module};
use ra_db::FileRange;
use ra_syntax::{ast::NameRef, TextRange, TextUnit};
use ra_text_edit::TextEdit;

pub(crate) use crate::assist_ctx::{Assist, AssistCtx};
pub use crate::assists::add_import::auto_import_text_edit;

/// Unique identifier of the assist, should not be shown to the user
/// directly.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct AssistId(pub &'static str);

#[derive(Debug, Clone)]
pub struct AssistLabel {
    /// Short description of the assist, as shown in the UI.
    pub label: String,
    pub id: AssistId,
}

#[derive(Debug, Clone)]
pub struct AssistAction {
    pub label: Option<String>,
    pub edit: TextEdit,
    pub cursor_position: Option<TextUnit>,
    pub target: Option<TextRange>,
}

#[derive(Debug, Clone)]
pub struct ResolvedAssist {
    pub label: AssistLabel,
    pub action_data: Either<AssistAction, Vec<AssistAction>>,
}

impl ResolvedAssist {
    pub fn get_first_action(&self) -> AssistAction {
        match &self.action_data {
            Either::Left(action) => action.clone(),
            Either::Right(actions) => actions[0].clone(),
        }
    }
}

/// Return all the assists applicable at the given position.
///
/// Assists are returned in the "unresolved" state, that is only labels are
/// returned, without actual edits.
pub fn applicable_assists<H>(db: &H, range: FileRange) -> Vec<AssistLabel>
where
    H: HirDatabase + 'static,
{
    AssistCtx::with_ctx(db, range, false, |ctx| {
        assists::all()
            .iter()
            .filter_map(|f| f(ctx.clone()))
            .map(|a| match a {
                Assist::Unresolved { label } => label,
                Assist::Resolved { .. } => unreachable!(),
            })
            .collect()
    })
}

/// A functionality for locating imports for the given name.
///
/// Currently has to be a trait with the real implementation provided by the ra_ide_api crate,
/// due to the search functionality located there.
/// Later, this trait should be removed completely and the search functionality moved to a separate crate,
/// accessible from the ra_assists crate.
pub trait ImportsLocator {
    /// Finds all imports for the given name and the module that contains this name.
    fn find_imports(
        &mut self,
        name_to_import: InFile<&NameRef>,
        module_with_name_to_import: Module,
    ) -> Option<Vec<ModPath>>;
}

/// Return all the assists applicable at the given position
/// and additional assists that need the imports locator functionality to work.
///
/// Assists are returned in the "resolved" state, that is with edit fully
/// computed.
pub fn assists_with_imports_locator<H, F>(
    db: &H,
    range: FileRange,
    mut imports_locator: F,
) -> Vec<ResolvedAssist>
where
    H: HirDatabase + 'static,
    F: ImportsLocator,
{
    AssistCtx::with_ctx(db, range, true, |ctx| {
        let mut assists = assists::all()
            .iter()
            .map(|f| f(ctx.clone()))
            .chain(
                assists::all_with_imports_locator()
                    .iter()
                    .map(|f| f(ctx.clone(), &mut imports_locator)),
            )
            .filter_map(std::convert::identity)
            .map(|a| match a {
                Assist::Resolved { assist } => assist,
                Assist::Unresolved { .. } => unreachable!(),
            })
            .collect();
        sort_assists(&mut assists);
        assists
    })
}

/// Return all the assists applicable at the given position.
///
/// Assists are returned in the "resolved" state, that is with edit fully
/// computed.
pub fn assists<H>(db: &H, range: FileRange) -> Vec<ResolvedAssist>
where
    H: HirDatabase + 'static,
{
    AssistCtx::with_ctx(db, range, true, |ctx| {
        let mut a = assists::all()
            .iter()
            .filter_map(|f| f(ctx.clone()))
            .map(|a| match a {
                Assist::Resolved { assist } => assist,
                Assist::Unresolved { .. } => unreachable!(),
            })
            .collect();
        sort_assists(&mut a);
        a
    })
}

fn sort_assists(assists: &mut Vec<ResolvedAssist>) {
    use std::cmp::Ordering;
    assists.sort_by(|a, b| match (a.get_first_action().target, b.get_first_action().target) {
        (Some(a), Some(b)) => a.len().cmp(&b.len()),
        (Some(_), None) => Ordering::Less,
        (None, Some(_)) => Ordering::Greater,
        (None, None) => Ordering::Equal,
    });
}

mod assists {
    use crate::{Assist, AssistCtx, ImportsLocator};
    use hir::db::HirDatabase;

    mod add_derive;
    mod add_explicit_type;
    mod add_impl;
    mod add_custom_impl;
    mod add_new;
    mod apply_demorgan;
    mod auto_import;
    mod invert_if;
    mod flip_comma;
    mod flip_binexpr;
    mod flip_trait_bound;
    mod change_visibility;
    mod fill_match_arms;
    mod merge_match_arms;
    mod introduce_variable;
    mod inline_local_variable;
    mod raw_string;
    mod replace_if_let_with_match;
    mod split_import;
    mod remove_dbg;
    pub(crate) mod add_import;
    mod add_missing_impl_members;
    mod move_guard;
    mod move_bounds;
    mod early_return;

    pub(crate) fn all<DB: HirDatabase>() -> &'static [fn(AssistCtx<DB>) -> Option<Assist>] {
        &[
            add_derive::add_derive,
            add_explicit_type::add_explicit_type,
            add_impl::add_impl,
            add_custom_impl::add_custom_impl,
            add_new::add_new,
            apply_demorgan::apply_demorgan,
            invert_if::invert_if,
            change_visibility::change_visibility,
            fill_match_arms::fill_match_arms,
            merge_match_arms::merge_match_arms,
            flip_comma::flip_comma,
            flip_binexpr::flip_binexpr,
            flip_trait_bound::flip_trait_bound,
            introduce_variable::introduce_variable,
            replace_if_let_with_match::replace_if_let_with_match,
            split_import::split_import,
            remove_dbg::remove_dbg,
            add_import::add_import,
            add_missing_impl_members::add_missing_impl_members,
            add_missing_impl_members::add_missing_default_members,
            inline_local_variable::inline_local_variable,
            move_guard::move_guard_to_arm_body,
            move_guard::move_arm_cond_to_match_guard,
            move_bounds::move_bounds_to_where_clause,
            raw_string::add_hash,
            raw_string::make_raw_string,
            raw_string::make_usual_string,
            raw_string::remove_hash,
            early_return::convert_to_guarded_return,
        ]
    }

    pub(crate) fn all_with_imports_locator<'a, DB: HirDatabase, F: ImportsLocator>(
    ) -> &'a [fn(AssistCtx<DB>, &mut F) -> Option<Assist>] {
        &[auto_import::auto_import]
    }
}

#[cfg(test)]
mod helpers {
    use ra_db::{fixture::WithFixture, FileRange};
    use ra_syntax::TextRange;
    use test_utils::{add_cursor, assert_eq_text, extract_offset, extract_range};

    use crate::{test_db::TestDB, Assist, AssistCtx, ImportsLocator};

    pub(crate) fn check_assist(
        assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
        before: &str,
        after: &str,
    ) {
        let (before_cursor_pos, before) = extract_offset(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange =
            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
        let assist =
            AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
        let action = match assist {
            Assist::Unresolved { .. } => unreachable!(),
            Assist::Resolved { assist } => assist.get_first_action(),
        };

        let actual = action.edit.apply(&before);
        let actual_cursor_pos = match action.cursor_position {
            None => action
                .edit
                .apply_to_offset(before_cursor_pos)
                .expect("cursor position is affected by the edit"),
            Some(off) => off,
        };
        let actual = add_cursor(&actual, actual_cursor_pos);
        assert_eq_text!(after, &actual);
    }

    pub(crate) fn check_assist_with_imports_locator<F: ImportsLocator>(
        assist: fn(AssistCtx<TestDB>, &mut F) -> Option<Assist>,
        imports_locator: &mut F,
        before: &str,
        after: &str,
    ) {
        let (before_cursor_pos, before) = extract_offset(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange =
            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
        let assist = AssistCtx::with_ctx(&db, frange, true, |ctx| assist(ctx, imports_locator))
            .expect("code action is not applicable");
        let action = match assist {
            Assist::Unresolved { .. } => unreachable!(),
            Assist::Resolved { assist } => assist.get_first_action(),
        };

        let actual = action.edit.apply(&before);
        let actual_cursor_pos = match action.cursor_position {
            None => action
                .edit
                .apply_to_offset(before_cursor_pos)
                .expect("cursor position is affected by the edit"),
            Some(off) => off,
        };
        let actual = add_cursor(&actual, actual_cursor_pos);
        assert_eq_text!(after, &actual);
    }

    pub(crate) fn check_assist_range(
        assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
        before: &str,
        after: &str,
    ) {
        let (range, before) = extract_range(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange = FileRange { file_id, range };
        let assist =
            AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
        let action = match assist {
            Assist::Unresolved { .. } => unreachable!(),
            Assist::Resolved { assist } => assist.get_first_action(),
        };

        let mut actual = action.edit.apply(&before);
        if let Some(pos) = action.cursor_position {
            actual = add_cursor(&actual, pos);
        }
        assert_eq_text!(after, &actual);
    }

    pub(crate) fn check_assist_target(
        assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
        before: &str,
        target: &str,
    ) {
        let (before_cursor_pos, before) = extract_offset(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange =
            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
        let assist =
            AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
        let action = match assist {
            Assist::Unresolved { .. } => unreachable!(),
            Assist::Resolved { assist } => assist.get_first_action(),
        };

        let range = action.target.expect("expected target on action");
        assert_eq_text!(&before[range.start().to_usize()..range.end().to_usize()], target);
    }

    pub(crate) fn check_assist_range_target(
        assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
        before: &str,
        target: &str,
    ) {
        let (range, before) = extract_range(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange = FileRange { file_id, range };
        let assist =
            AssistCtx::with_ctx(&db, frange, true, assist).expect("code action is not applicable");
        let action = match assist {
            Assist::Unresolved { .. } => unreachable!(),
            Assist::Resolved { assist } => assist.get_first_action(),
        };

        let range = action.target.expect("expected target on action");
        assert_eq_text!(&before[range.start().to_usize()..range.end().to_usize()], target);
    }

    pub(crate) fn check_assist_not_applicable(
        assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
        before: &str,
    ) {
        let (before_cursor_pos, before) = extract_offset(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange =
            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
        let assist = AssistCtx::with_ctx(&db, frange, true, assist);
        assert!(assist.is_none());
    }

    pub(crate) fn check_assist_with_imports_locator_not_applicable<F: ImportsLocator>(
        assist: fn(AssistCtx<TestDB>, &mut F) -> Option<Assist>,
        imports_locator: &mut F,
        before: &str,
    ) {
        let (before_cursor_pos, before) = extract_offset(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange =
            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
        let assist = AssistCtx::with_ctx(&db, frange, true, |ctx| assist(ctx, imports_locator));
        assert!(assist.is_none());
    }

    pub(crate) fn check_assist_range_not_applicable(
        assist: fn(AssistCtx<TestDB>) -> Option<Assist>,
        before: &str,
    ) {
        let (range, before) = extract_range(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange = FileRange { file_id, range };
        let assist = AssistCtx::with_ctx(&db, frange, true, assist);
        assert!(assist.is_none());
    }
}

#[cfg(test)]
mod tests {
    use ra_db::{fixture::WithFixture, FileRange};
    use ra_syntax::TextRange;
    use test_utils::{extract_offset, extract_range};

    use crate::test_db::TestDB;

    #[test]
    fn assist_order_field_struct() {
        let before = "struct Foo { <|>bar: u32 }";
        let (before_cursor_pos, before) = extract_offset(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange =
            FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
        let assists = super::assists(&db, frange);
        let mut assists = assists.iter();

        assert_eq!(
            assists.next().expect("expected assist").label.label,
            "Change visibility to pub(crate)"
        );
        assert_eq!(assists.next().expect("expected assist").label.label, "Add `#[derive]`");
    }

    #[test]
    fn assist_order_if_expr() {
        let before = "
        pub fn test_some_range(a: int) -> bool {
            if let 2..6 = <|>5<|> {
                true
            } else {
                false
            }
        }";
        let (range, before) = extract_range(before);
        let (db, file_id) = TestDB::with_single_file(&before);
        let frange = FileRange { file_id, range };
        let assists = super::assists(&db, frange);
        let mut assists = assists.iter();

        assert_eq!(assists.next().expect("expected assist").label.label, "Extract into variable");
        assert_eq!(assists.next().expect("expected assist").label.label, "Replace with match");
    }
}