//! Mutators related to the start section.

use super::Mutator;

use crate::{Result, WasmMutate};

use wasm_encoder::Module;

/// A mutator to remove the start section.

#[derive(Clone, Copy)]

pub struct RemoveStartSection;

impl Mutator for RemoveStartSection {

    fn can_mutate(&self, config: &WasmMutate) -> bool {

        !config.preserve_semantics && config.info().start.is_some()

    }

    fn mutate<'a>(

        &self,

        config: &'a mut WasmMutate,

    ) -> Result<Box<dyn Iterator<Item = crate::Result<Module>> + 'a>> {

        let mut module = Module::new();

        let start_section_index = config.info().start.unwrap();

        for (i, section) in config.info().raw_sections.iter().enumerate() {

            if i == start_section_index {

                continue;

            }

            module.section(section);

        }

        Ok(Box::new(std::iter::once(Ok(module))))

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn test_remove_start_segment() {

        crate::mutators::match_mutation(

            r#"

                (module

                    (func $f (param i32) (result i32)

                        local.get 0

                    )

                    (start $f)

                )

            "#,

            RemoveStartSection,

            r#"

                (module

                    (func $f (param i32) (result i32)

                        local.get 0

                    )

                )

            "#,

        );

    }

}