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/*
 * Copyright 2018 The Starlark in Rust Authors.
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

//! Implementation of iterators for string type.

use derive_more::Display;
use gazebo::{any::AnyLifetime, coerce::Coerce};

use crate as starlark;
use crate::values::{Heap, StarlarkValue, Value, ValueLike};

/// An opaque iterator over a string, produced by elems/codepoints
#[derive(Debug, Trace, Coerce, Display, Freeze, NoSerialize, AnyLifetime)]
#[display(fmt = "iterator")]
#[repr(C)]
struct StringIteratorGen<V> {
    string: V,
    produce_char: bool, // if not char, then int
}

pub(crate) fn iterate_chars<'v>(string: Value<'v>, heap: &'v Heap) -> Value<'v> {
    heap.alloc(StringIterator {
        string,
        produce_char: true,
    })
}

pub(crate) fn iterate_codepoints<'v>(string: Value<'v>, heap: &'v Heap) -> Value<'v> {
    heap.alloc(StringIterator {
        string,
        produce_char: false,
    })
}

starlark_complex_value!(StringIterator);

impl<'v, T: ValueLike<'v>> StarlarkValue<'v> for StringIteratorGen<T>
where
    Self: AnyLifetime<'v>,
{
    starlark_type!("iterator");

    fn iterate<'a>(
        &'a self,
        heap: &'v Heap,
    ) -> anyhow::Result<Box<dyn Iterator<Item = Value<'v>> + 'a>>
    where
        'v: 'a,
    {
        let s = self.string.to_value().unpack_str().unwrap().chars();
        if self.produce_char {
            Ok(box s.map(move |x| heap.alloc(x)))
        } else {
            Ok(box s.map(|x| Value::new_int(u32::from(x) as i32)))
        }
    }

    fn with_iterator(
        &self,
        heap: &'v Heap,
        f: &mut dyn FnMut(&mut dyn Iterator<Item = Value<'v>>) -> anyhow::Result<()>,
    ) -> anyhow::Result<()> {
        let s = self.string.to_value().unpack_str().unwrap().chars();
        if self.produce_char {
            f(&mut s.map(|x| heap.alloc(x)))
        } else {
            f(&mut s.map(|x| Value::new_int(u32::from(x) as i32)))
        }
    }
}