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use super::{ModuleError, ModuleValidator};
use parity_wasm::elements::Module;

/// Struct on which ModuleValidator is implemented.
pub struct CheckStartFunc {
    start_required: bool,
}

impl CheckStartFunc {
    pub fn new(is_start_required: bool) -> Self {
        CheckStartFunc {
            start_required: is_start_required,
        }
    }
}

impl ModuleValidator for CheckStartFunc {
    fn validate(&self, module: &Module) -> Result<bool, ModuleError> {
        Ok(module.start_section().is_some() == self.start_required)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use parity_wasm::elements::deserialize_buffer;

    #[test]
    fn start_required_good() {
        let wasm: Vec<u8> = vec![
            0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x04, 0x01, 0x60, 0x00, 0x00,
            0x03, 0x02, 0x01, 0x00, 0x07, 0x08, 0x01, 0x04, 0x6d, 0x61, 0x69, 0x6e, 0x00, 0x00,
            0x08, 0x01, 0x00, 0x0a, 0x04, 0x01, 0x02, 0x00, 0x0b,
        ];

        let module = deserialize_buffer::<Module>(&wasm).unwrap();
        let checker = CheckStartFunc::new(true);

        let result = checker.validate(&module).unwrap();
        assert_eq!(true, result);
    }

    #[test]
    fn start_required_bad() {
        let wasm: Vec<u8> = vec![
            0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x04, 0x01, 0x60, 0x00, 0x00,
            0x03, 0x02, 0x01, 0x00, 0x07, 0x08, 0x01, 0x04, 0x6d, 0x61, 0x69, 0x6e, 0x00, 0x00,
            0x08, 0x01, 0x00, 0x0a, 0x04, 0x01, 0x02, 0x00, 0x0b,
        ];

        let module = deserialize_buffer::<Module>(&wasm).unwrap();
        let checker = CheckStartFunc::new(false);

        let result = checker.validate(&module).unwrap();
        assert_eq!(false, result);
    }

    #[test]
    fn start_not_required_good() {
        let wasm: Vec<u8> = vec![
            0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x04, 0x01, 0x60, 0x00, 0x00,
            0x03, 0x02, 0x01, 0x00, 0x07, 0x08, 0x01, 0x04, 0x6d, 0x61, 0x69, 0x6e, 0x00, 0x00,
            0x0a, 0x04, 0x01, 0x02, 0x00, 0x0b,
        ];

        let module = deserialize_buffer::<Module>(&wasm).unwrap();
        let checker = CheckStartFunc::new(false);

        let result = checker.validate(&module).unwrap();
        assert_eq!(true, result);
    }

    #[test]
    fn start_not_required_bad() {
        let wasm: Vec<u8> = vec![
            0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00, 0x01, 0x04, 0x01, 0x60, 0x00, 0x00,
            0x03, 0x02, 0x01, 0x00, 0x07, 0x08, 0x01, 0x04, 0x6d, 0x61, 0x69, 0x6e, 0x00, 0x00,
            0x0a, 0x04, 0x01, 0x02, 0x00, 0x0b,
        ];

        let module = deserialize_buffer::<Module>(&wasm).unwrap();
        let checker = CheckStartFunc::new(true);

        let result = checker.validate(&module).unwrap();
        assert_eq!(false, result);
    }
}