use parity_wasm::elements;

use crate::optimizer::{global_section, export_section};

/// Export all declared mutable globals.
///
/// This will export all internal mutable globals under the name of
/// concat(`prefix`, i) where i is the index inside the range of
/// [0..<total number of internal mutable globals>].
pub fn export_mutable_globals(
	module: &mut elements::Module,
	prefix: impl Into<String>,
) {

	let exports = global_section(module).map(
		|section| section.entries().iter().enumerate().filter_map(
			|(index, global)| if global.global_type().is_mutable() { Some(index) } else { None }
		).collect::<Vec<_>>()
	).unwrap_or_default();

	if module.export_section().is_none() {
		module.sections_mut().push(elements::Section::Export(elements::ExportSection::default()));
	}

	let mut symbol_index = 0usize;
	let prefix: String = prefix.into();
	for export in exports {
		let new_entry = elements::ExportEntry::new(
			format!("{}_{}", prefix, symbol_index),
			elements::Internal::Global(
				(module.import_count(elements::ImportCountType::Global) + export) as _
			),
		);
		export_section(module)
			.expect("added above if does not exists")
			.entries_mut()
			.push(new_entry);
		symbol_index += 1;
	}
}

#[cfg(test)]
mod tests {

	use super::export_mutable_globals;
	use parity_wasm::elements;

	fn parse_wat(source: &str) -> elements::Module {
		let module_bytes = wabt::Wat2Wasm::new()
			.validate(true)
			.convert(source)
			.expect("failed to parse module");
		elements::deserialize_buffer(module_bytes.as_ref())
			.expect("failed to parse module")
	}

	macro_rules! test_export_global {
		(name = $name:ident; input = $input:expr; expected = $expected:expr) => {
			#[test]
			fn $name() {
				let mut input_module = parse_wat($input);
				let expected_module = parse_wat($expected);

				export_mutable_globals(&mut input_module, "exported_internal_global");

				let actual_bytes = elements::serialize(input_module)
					.expect("injected module must have a function body");

				let expected_bytes = elements::serialize(expected_module)
					.expect("injected module must have a function body");

				assert_eq!(actual_bytes, expected_bytes);
			}
		}
	}

	test_export_global! {
		name = simple;
		input = r#"
		(module
			(global (;0;) (mut i32) (i32.const 1))
			(global (;1;) (mut i32) (i32.const 0)))
		"#;
		expected = r#"
		(module
			(global (;0;) (mut i32) (i32.const 1))
			(global (;1;) (mut i32) (i32.const 0))
			(export "exported_internal_global_0" (global 0))
			(export "exported_internal_global_1" (global 1)))
		"#
	}

	test_export_global! {
		name = with_import;
		input = r#"
		(module
			(import "env" "global" (global $global i64))
			(global (;0;) (mut i32) (i32.const 1))
			(global (;1;) (mut i32) (i32.const 0)))
		"#;
		expected = r#"
		(module
			(import "env" "global" (global $global i64))
			(global (;0;) (mut i32) (i32.const 1))
			(global (;1;) (mut i32) (i32.const 0))
			(export "exported_internal_global_0" (global 1))
			(export "exported_internal_global_1" (global 2)))
		"#
	}

	test_export_global! {
		name = with_import_and_some_are_immutable;
		input = r#"
		(module
			(import "env" "global" (global $global i64))
			(global (;0;) i32 (i32.const 1))
			(global (;1;) (mut i32) (i32.const 0)))
		"#;
		expected = r#"
		(module
			(import "env" "global" (global $global i64))
			(global (;0;) i32 (i32.const 1))
			(global (;1;) (mut i32) (i32.const 0))
			(export "exported_internal_global_0" (global 2)))
		"#
	}
}