more parsing helpers

1 files changed, 92 insertions, 0 deletions

diff --git a/src/object/parser.rs b/src/object/parser.rs
new file mode 100644
index 0000000..5879e9a
--- /dev/null
+++ b/src/object/parser.rs
@@ -0,0 +1,92 @@
+use super::Value;
+use anyhow::{Context, Result, anyhow, bail};
+use std::collections::BTreeMap;
+
+pub trait FromValue: Sized {
+    fn from_value(v: Value) -> Result<Self>;
+}
+
+impl Value {
+    pub fn parse<T: FromValue>(self) -> Result<T> {
+        T::from_value(self)
+    }
+    pub fn as_class(self, name: &'static str) -> Result<Fields> {
+        if let Value::Object { class, fields } = self {
+            if class == name {
+                Ok(Fields {
+                    class: name,
+                    fields,
+                })
+            } else {
+                bail!("expected class {name} but found {class}")
+            }
+        } else {
+            bail!("expected class {name}")
+        }
+    }
+}
+
+pub struct Fields {
+    class: &'static str,
+    fields: BTreeMap<String, Value>,
+}
+
+impl Fields {
+    pub fn field<T: FromValue>(&mut self, name: &str) -> Result<T> {
+        self.fields
+            .remove(name)
+            .ok_or(anyhow!("expected {name} field in {}", self.class))?
+            .parse()
+            .context(anyhow!("in {}.{name} field", self.class))
+    }
+    pub fn remove(&mut self, key: &str) -> Option<Value> {
+        self.fields.remove(key)
+    }
+}
+
+impl FromValue for u8 {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_u8().ok_or(anyhow!("expected u8"))
+    }
+}
+impl FromValue for u16 {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_u16().ok_or(anyhow!("expected u16"))
+    }
+}
+impl FromValue for f32 {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_f32().ok_or(anyhow!("expected f32"))
+    }
+}
+impl FromValue for u32 {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_u32().ok_or(anyhow!("expected u32"))
+    }
+}
+impl FromValue for i32 {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_i32().ok_or(anyhow!("expected i32"))
+    }
+}
+impl FromValue for u64 {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_u64().ok_or(anyhow!("expected u64"))
+    }
+}
+impl FromValue for bool {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_bool().ok_or(anyhow!("expected bool"))
+    }
+}
+impl FromValue for String {
+    fn from_value(v: Value) -> anyhow::Result<Self> {
+        v.as_string().ok_or(anyhow!("expected string"))
+    }
+}
+
+impl Value {
+    pub fn as_vector(self) -> Option<Vec<Value>> {
+        self.as_class("vector").ok()?.remove("Array")?.as_array()
+    }
+}