1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151

use crate::entity::Browsable;
use crate::entity::BrowseResult;
use serde::de::DeserializeOwned;
use std::fmt;
use std::marker::PhantomData;

use serde::de::{self, Deserialize, Deserializer, MapAccess, SeqAccess, Visitor};

// Browse result fields in musicbrainz api v2 are prefixed with resource type :
// this impl provide a generic browse result deserializer
impl<'de, T> Deserialize<'de> for BrowseResult<T>
where
    T: DeserializeOwned + Browsable,
{
    fn deserialize<D>(deserializer: D) -> Result<BrowseResult<T>, D::Error>
    where
        D: Deserializer<'de>,
        T: Browsable,
    {
        enum Field<T> {
            Count,
            Offset,
            Entities(PhantomData<T>),
        };

        impl<'de, T> Deserialize<'de> for Field<T>
        where
            T: Browsable,
        {
            fn deserialize<D>(deserializer: D) -> Result<Field<T>, D::Error>
            where
                D: Deserializer<'de>,
                T: Browsable,
            {
                struct FieldVisitor<T>(PhantomData<T>);

                impl<'de, T> Visitor<'de> for FieldVisitor<T>
                where
                    T: Browsable,
                {
                    type Value = Field<T>;

                    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                        formatter.write_str("`count` or `offset`, `entities`")
                    }

                    fn visit_str<E>(self, value: &str) -> Result<Field<T>, E>
                    where
                        E: de::Error,
                        T: Browsable,
                    {
                        match value {
                            field if field == T::COUNT_FIELD => Ok(Field::Count),
                            field if field == T::OFFSET_FIELD => Ok(Field::Offset),
                            field if field == T::ENTITIES_FIELD => {
                                Ok(Field::Entities(PhantomData::<T>))
                            }
                            _ => Err(de::Error::unknown_field(value, FIELDS)),
                        }
                    }
                }

                deserializer.deserialize_identifier(FieldVisitor(PhantomData::<T>))
            }
        }

        struct BrowseResultVisitor<T> {
            phatom: PhantomData<T>,
        };

        impl<'de, T> Visitor<'de> for BrowseResultVisitor<T>
        where
            T: Browsable + Deserialize<'de>,
        {
            type Value = BrowseResult<T>;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                formatter.write_str("struct Browsable<T>")
            }

            fn visit_seq<V>(self, mut seq: V) -> Result<BrowseResult<T>, V::Error>
            where
                V: SeqAccess<'de>,
            {
                let count = seq
                    .next_element()?
                    .ok_or_else(|| de::Error::invalid_length(0, &self))?;
                let offset = seq
                    .next_element()?
                    .ok_or_else(|| de::Error::invalid_length(1, &self))?;
                let entities = seq
                    .next_element()?
                    .ok_or_else(|| de::Error::invalid_length(2, &self))?;
                Ok(BrowseResult {
                    count,
                    offset,
                    entities,
                })
            }

            fn visit_map<V>(self, mut map: V) -> Result<BrowseResult<T>, V::Error>
            where
                T: Browsable + Deserialize<'de>,
                V: MapAccess<'de>,
            {
                let mut count: Option<i32> = None;
                let mut offset: Option<i32> = None;
                let mut entities: Option<Vec<T>> = None;
                while let Some(key) = map.next_key::<Field<T>>()? {
                    match key {
                        Field::Count => {
                            if count.is_some() {
                                return Err(de::Error::duplicate_field("count"));
                            }
                            count = Some(map.next_value()?);
                        }
                        Field::Offset => {
                            if offset.is_some() {
                                return Err(de::Error::duplicate_field("offset"));
                            }
                            offset = Some(map.next_value()?);
                        }
                        Field::Entities(_t) => {
                            if entities.is_some() {
                                return Err(de::Error::duplicate_field("entities"));
                            }
                            entities = Some(map.next_value()?);
                        }
                    }
                }
                let count = count.ok_or_else(|| de::Error::missing_field("count"))?;
                let offset = offset.ok_or_else(|| de::Error::missing_field("offset"))?;
                let entities = entities.ok_or_else(|| de::Error::missing_field("entities"))?;
                Ok(BrowseResult {
                    count,
                    offset,
                    entities,
                })
            }
        }
        const FIELDS: &[&str] = &["count", "offset", "artists"];

        deserializer.deserialize_struct(
            "BrowseResult",
            FIELDS,
            BrowseResultVisitor {
                phatom: PhantomData::<T>,
            },
        )
    }
}