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use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize, Clone, Debug, Eq, PartialEq)]
#[allow(clippy::module_name_repetitions)]
pub struct Meta<'a> {
    pub app_id:      &'a str,
    /// App name is shown in the launcher in the list of apps.
    pub app_name:    &'a str,
    pub author_id:   &'a str,
    pub author_name: &'a str,
    /// Launcher is the app that starts first when runtime is launched.
    pub launcher:    bool,
    /// Let the app to use privileged and dangerous runtime API.
    pub sudo:        bool,
    /// The ever-incrementing version number of the app build.
    /// Used by netplay to ensure both devices running the same version.
    pub version:     i32,
}

impl<'a> Meta<'a> {
    /// Load metadata from bytes generated by [`Meta::encode`].
    ///
    /// # Errors
    ///
    /// May return an error if the buffer does not contain valid metadata.
    pub fn decode(s: &'a [u8]) -> Result<Self, postcard::Error> {
        postcard::from_bytes(s)
    }

    /// Encode the matadata using the buffer.
    ///
    /// The buffer is required to avoid allocations on the crate side.
    /// Use [`Meta::size`] to calculate the required buffer size.
    ///
    /// # Errors
    ///
    /// May return an error if the buffer is no big enough.
    pub fn encode<'b>(&self, buf: &'b mut [u8]) -> Result<&'b mut [u8], postcard::Error> {
        postcard::to_slice(self, buf)
    }

    /// Calculate the buffer size required to encode the meta.
    #[must_use]
    #[allow(clippy::missing_panics_doc)]
    pub fn size(&self) -> usize {
        let flavor = postcard::ser_flavors::Size::default();
        postcard::serialize_with_flavor(self, flavor).unwrap()
    }
}

/// A struct with only a few safe fields from Meta.
///
/// It is used to serialize information about an app outside of the app dir.
/// Since it is outside, it escapes the hash and signature checks
/// and so it must not store any information that must be verified before use.
#[derive(Serialize, Deserialize, Clone, Debug, Eq, PartialEq)]
#[allow(clippy::module_name_repetitions)]
pub struct ShortMeta<'a> {
    pub app_id:    &'a str,
    pub author_id: &'a str,
}

impl<'a> ShortMeta<'a> {
    /// Load metadata from bytes generated by [`ShortMeta::encode`].
    ///
    /// # Errors
    ///
    /// May return an error if the buffer does not contain valid metadata.
    pub fn decode(s: &'a [u8]) -> Result<Self, postcard::Error> {
        postcard::from_bytes(s)
    }

    /// Encode the matadata using the buffer.
    ///
    /// The buffer is required to avoid allocations on the crate side.
    /// Use [`ShortMeta::size`] to calculate the required buffer size.
    ///
    /// # Errors
    ///
    /// May return an error if the buffer is no big enough.
    pub fn encode<'b>(&self, buf: &'b mut [u8]) -> Result<&'b mut [u8], postcard::Error> {
        postcard::to_slice(self, buf)
    }

    /// Calculate the buffer size required to encode the meta.
    #[must_use]
    #[allow(clippy::missing_panics_doc)]
    pub fn size(&self) -> usize {
        let flavor = postcard::ser_flavors::Size::default();
        postcard::serialize_with_flavor(self, flavor).unwrap()
    }
}

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

    #[test]
    fn test_roundtrip() {
        let given = Meta {
            app_id:      "some-app-id",
            app_name:    "Some App Name",
            author_id:   "some-author-id",
            author_name: "Some Author Name",
            launcher:    false,
            sudo:        false,
            version:     12,
        };
        let mut buf = vec![0; given.size()];
        let raw = given.encode(&mut buf).unwrap();
        let actual = Meta::decode(raw).unwrap();
        assert_eq!(given, actual);
    }
}