#[macro_use]
extern crate serde_derive; // 1.0.70
extern crate serde; // 1.0.70
extern crate serde_json; // 1.0.24

use serde::de::{Deserialize, Deserializer, SeqAccess, Visitor};
use std::fmt;

static mut AGE_UPTO: u64 = 0;

#[derive(Deserialize)]
struct Person {
    age: u64,
    name: String,
}

struct OldestUpTo {
    age: u64,
    list: Vec<Person>,
}

impl<'de> Deserialize<'de> for OldestUpTo {
    fn deserialize<D>(deserializer: D) -> Result<OldestUpTo, D::Error>
    where
        D: Deserializer<'de>,
    {
        //
        struct OldestUpToVisitor;

        impl<'de> Visitor<'de> for OldestUpToVisitor {
            type Value = OldestUpTo;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                formatter.write_str("an array of objects")
            }

            fn visit_seq<V>(self, mut seq: V) -> Result<OldestUpTo, V::Error>
            where
                V: SeqAccess<'de>,
            {
                let mut oldest = OldestUpTo {
                    age: 0,
                    list: vec![],
                };

                while let Some(person) = seq.next_element::<Person>()? {
                    if person.age <= unsafe { AGE_UPTO } && person.age > oldest.age {
                        oldest.age = person.age;
                        oldest.list.clear();
                        oldest.list.push(person);
                    } else if person.age == oldest.age {
                        oldest.list.push(person);
                    }
                }

                Ok(oldest)
            }
        }

        deserializer.deserialize_seq(OldestUpToVisitor)
    }
}

fn main() {
    let json = r#"[
        {
            "age": 42,
            "name": "André"
        },
        {
            "age": 53,
            "name": "Bruno"
        },
        {
            "age": 53,
            "name": "Carlos"
        },
        {
            "age": 52,
            "name": "Diego"
        },
        {
            "age": 59,
            "name": "Eduardo"
        }
    ]"#;

    unsafe {
        AGE_UPTO = 55;
    }
    let oldest: OldestUpTo = serde_json::from_str(json).unwrap();

    for p in oldest.list {
        println!("Age: {}, Name: {}", p.age, p.name);
    }
}