use std::collections::HashMap;
use std::fmt::Formatter;
use std::marker::PhantomData;
use serde::{Deserialize, Deserializer};
use serde::de::{MapAccess, Visitor};
use sha1_smol::Digest;

#[derive(Debug, Deserialize)]
pub struct Asset {
    #[serde(skip)]
    pub name: String,
    pub hash: Digest,
    pub size: usize
}

#[derive(Debug, Deserialize)]
pub struct AssetIndex {
    #[serde(rename = "virtual", default)]
    pub virtual_assets: bool,
    #[serde(default)]
    pub map_to_resources: bool,

    #[serde(deserialize_with = "deserialize_assets")]
    pub objects: HashMap<String, Asset>
}

trait SetName {
    fn set_name(&mut self, name: String);
}

impl SetName for Asset {
    fn set_name(&mut self, name: String) {
        self.name = name;
    }
}

fn deserialize_assets<'de, D, T>(deserializer: D) -> Result<HashMap<String, T>, D::Error>
where
    D: Deserializer<'de>,
    T: SetName + Deserialize<'de>
{
    struct AssetVisitor<T>(PhantomData<T>);

    impl<'de, T> Visitor<'de> for AssetVisitor<T>
    where
        T: SetName + Deserialize<'de>
    {
        type Value = HashMap<String, T>;

        fn expecting(&self, formatter: &mut Formatter) -> std::fmt::Result {
            formatter.write_str("asset objects map")
        }

        fn visit_map<A>(self, mut map: A) -> Result<Self::Value, A::Error>
        where
            A: MapAccess<'de>,
        {
            let mut out = HashMap::new();

            while let Some((key, mut asset)) = map.next_entry::<String, T>()? {
                asset.set_name(key.clone());
                out.insert(key, asset);
            }

            Ok(out)
        }
    }

    deserializer.deserialize_any(AssetVisitor(PhantomData))
}

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

    #[test]
    fn test_it() {
        dbg!(serde_json::from_str::<AssetIndex>(r#"{
            "virtual": true,
            "objects": {
                "object1": { "hash": "0d000710b71ca9aafabd8f587768431d0b560b32", "size": 100 },
                "object2/abc": { "hash": "0e000710b71ca9aafabd8f587768431d0b560b32", "size": 10000 }
            }
        }"#).unwrap());
    }
}