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use c2rust_ast_builder::{mk, Builder};
use indexmap::{IndexMap, IndexSet};
use syntax::ast::{ForeignItem, Item};
use syntax::ptr::P;

use std::borrow::Cow;
use std::mem::swap;

#[derive(Debug)]
pub struct MultiImport {
    attrs: Option<Builder>,
    leaves: IndexSet<String>,
}

impl MultiImport {
    fn new() -> Self {
        MultiImport {
            attrs: None,
            leaves: IndexSet::new(),
        }
    }

    pub fn insert<'a, S>(&mut self, leaf: S)
    where
        S: Into<Cow<'a, str>>,
    {
        self.leaves.insert(leaf.into().into_owned());
    }

    pub fn insert_with_attr<'a, S>(&mut self, leaf: S, attrs: Builder)
    where
        S: Into<Cow<'a, str>>,
    {
        self.insert(leaf);
        self.attrs = Some(attrs);
    }
}

#[derive(Debug)]
pub struct PathedMultiImports(IndexMap<Vec<String>, MultiImport>);

impl PathedMultiImports {
    pub fn new() -> Self {
        PathedMultiImports(IndexMap::new())
    }

    pub fn get_mut(&mut self, path: Vec<String>) -> &mut MultiImport {
        self.0.entry(path).or_insert(MultiImport::new())
    }

    pub fn into_items(self) -> Vec<P<Item>> {
        fn build_items((path, imports): (Vec<String>, MultiImport)) -> P<Item> {
            imports
                .attrs
                .unwrap_or_else(|| mk())
                .use_multiple_item(path, imports.leaves.iter().collect())
        }

        self.0.into_iter().map(build_items).collect()
    }
}

#[derive(Debug)]
pub struct ItemStore {
    pub items: Vec<P<Item>>,
    pub foreign_items: Vec<ForeignItem>,
    pub uses: PathedMultiImports,
}

impl ItemStore {
    pub fn new() -> Self {
        ItemStore {
            items: Vec::new(),
            foreign_items: Vec::new(),
            uses: PathedMultiImports::new(),
        }
    }

    pub fn drain(&mut self) -> (Vec<P<Item>>, Vec<ForeignItem>, PathedMultiImports) {
        let mut items = Vec::new();
        let mut foreign_items = Vec::new();
        let mut uses = PathedMultiImports::new();

        swap(&mut items, &mut self.items);
        swap(&mut foreign_items, &mut self.foreign_items);
        swap(&mut uses, &mut self.uses);

        (items, foreign_items, uses)
    }
}