flatland_protocol/
codec.rs

1use serde::{de::DeserializeOwned, Serialize};
2
3use crate::Envelope;
4
5#[derive(Debug, thiserror::Error)]
6pub enum CodecError {
7    #[error("postcard encode failed: {0}")]
8    PostcardEncode(postcard::Error),
9    #[error("postcard decode failed: {0}")]
10    PostcardDecode(postcard::Error),
11    #[error("bincode encode failed: {0}")]
12    BincodeEncode(bincode::Error),
13    #[error("bincode decode failed: {0}")]
14    BincodeDecode(bincode::Error),
15}
16
17pub trait Codec {
18    fn encode<T: Serialize>(&self, value: &T) -> Result<Vec<u8>, CodecError>;
19    fn decode<T: DeserializeOwned>(&self, bytes: &[u8]) -> Result<T, CodecError>;
20}
21
22/// Default on-wire codec for game traffic (compact, serde-native).
23#[derive(Debug, Clone, Copy, Default)]
24pub struct PostcardCodec;
25
26impl Codec for PostcardCodec {
27    fn encode<T: Serialize>(&self, value: &T) -> Result<Vec<u8>, CodecError> {
28        postcard::to_allocvec(value).map_err(CodecError::PostcardEncode)
29    }
30
31    fn decode<T: DeserializeOwned>(&self, bytes: &[u8]) -> Result<T, CodecError> {
32        postcard::from_bytes(bytes).map_err(CodecError::PostcardDecode)
33    }
34}
35
36/// Alternative codec used in benchmarks and for comparison.
37#[derive(Debug, Clone, Copy, Default)]
38pub struct BincodeCodec;
39
40impl Codec for BincodeCodec {
41    fn encode<T: Serialize>(&self, value: &T) -> Result<Vec<u8>, CodecError> {
42        bincode::serialize(value).map_err(CodecError::BincodeEncode)
43    }
44
45    fn decode<T: DeserializeOwned>(&self, bytes: &[u8]) -> Result<T, CodecError> {
46        bincode::deserialize(bytes).map_err(CodecError::BincodeDecode)
47    }
48}
49
50pub fn encode_envelope<T: Serialize>(codec: &impl Codec, payload: T) -> Result<Vec<u8>, CodecError> {
51    codec.encode(&Envelope::new(payload))
52}
53
54pub fn decode_envelope<T: DeserializeOwned>(
55    codec: &impl Codec,
56    bytes: &[u8],
57) -> Result<Envelope<T>, CodecError> {
58    codec.decode(bytes)
59}
60
61#[cfg(test)]
62mod tests {
63    use super::*;
64    use crate::types::{
65        BlueprintIngredientView, BlueprintView, EntityState, TickDelta, ToolRequirementView,
66        Transform, WorldCoord,
67    };
68
69    fn sample_tick_delta() -> TickDelta {
70        TickDelta {
71            tick: 42,
72            entities: (0..15)
73                .map(|i| EntityState {
74                    id: i + 1,
75                    label: String::new(),
76                    transform: Transform {
77                        position: WorldCoord::surface(i as f32, i as f32 * 0.5),
78                        yaw: 1.25,
79                        velocity: crate::types::Velocity2D { vx: 0.5, vy: -0.2 },
80                    },
81                    vitals: None,
82                    inside_building: None,
83                })
84                .collect(),
85            resource_nodes: Vec::new(),
86            buildings: Vec::new(),
87            doors: Vec::new(),
88            npcs: Vec::new(),
89            inventory: Vec::new(),
90            blueprints: Vec::new(),
91        }
92    }
93
94    #[test]
95    fn postcard_blueprint_snapshot_roundtrip() {
96        let codec = PostcardCodec;
97        let delta = TickDelta {
98            tick: 1,
99            entities: vec![],
100            resource_nodes: vec![],
101            buildings: vec![],
102            doors: vec![],
103            npcs: vec![],
104            inventory: vec![],
105            blueprints: vec![BlueprintView {
106                id: "oak_to_lumber".into(),
107                label: "Saw Planks".into(),
108                output: "lumber".into(),
109                output_qty: 1,
110                craft_ticks: 60,
111                station: Some("woodworking".into()),
112                category: Some("woodworking".into()),
113                required_tools: vec![ToolRequirementView {
114                    item: "handsaw".into(),
115                    consumed: false,
116                }],
117                skill: None,
118                failure_chance: 0.0,
119                inputs: vec![BlueprintIngredientView {
120                    template_id: "oak_log".into(),
121                    quantity: 2,
122                    consumed: true,
123                }],
124            }],
125        };
126        let bytes = codec.encode(&Envelope::new(delta.clone())).unwrap();
127        let decoded: Envelope<TickDelta> = codec.decode(&bytes).unwrap();
128        assert_eq!(decoded.payload, delta);
129    }
130
131    #[test]
132    fn postcard_roundtrip_tick_delta() {
133        let codec = PostcardCodec;
134        let original = Envelope::new(sample_tick_delta());
135        let bytes = codec.encode(&original).expect("encode");
136        let decoded: Envelope<TickDelta> = codec.decode(&bytes).expect("decode");
137        assert_eq!(original, decoded);
138    }
139
140    #[test]
141    fn bincode_roundtrip_tick_delta() {
142        let codec = BincodeCodec;
143        let original = Envelope::new(sample_tick_delta());
144        let bytes = codec.encode(&original).expect("encode");
145        let decoded: Envelope<TickDelta> = codec.decode(&bytes).expect("decode");
146        assert_eq!(original, decoded);
147    }
148
149    #[test]
150    fn postcard_many_entities_vitals_none() {
151        let delta = TickDelta {
152            tick: 42,
153            entities: (0..15)
154                .map(|i| EntityState {
155                    id: i + 1,
156                    label: String::new(),
157                    transform: Transform {
158                        position: WorldCoord::surface(i as f32, i as f32 * 0.5),
159                        yaw: 1.25,
160                        velocity: crate::types::Velocity2D { vx: 0.5, vy: -0.2 },
161                    },
162                    vitals: None,
163                    inside_building: None,
164                })
165                .collect(),
166            resource_nodes: vec![],
167            buildings: vec![],
168            doors: vec![],
169            npcs: vec![],
170            inventory: vec![],
171            blueprints: vec![],
172        };
173        let codec = PostcardCodec;
174        let bytes = codec.encode(&Envelope::new(delta.clone())).unwrap();
175        let decoded: Envelope<TickDelta> = codec.decode(&bytes).unwrap();
176        assert_eq!(decoded.payload, delta);
177    }
178}
flatland_protocol/codec.rs

flatland_protocol/
codec.rs
