Extract methods into separate module

1 files changed, 119 insertions, 0 deletions

diff --git a/src/eval/methods.rs b/src/eval/methods.rs
new file mode 100644
index 00000000..017591b4
--- /dev/null
+++ b/src/eval/methods.rs
@@ -0,0 +1,119 @@
+//! Methods on values.
+
+use super::{Args, StrExt, Value};
+use crate::diag::{At, TypResult};
+use crate::syntax::Span;
+use crate::Context;
+
+/// Call a method on a value.
+pub fn call(
+    ctx: &mut Context,
+    value: Value,
+    method: &str,
+    mut args: Args,
+    span: Span,
+) -> TypResult<Value> {
+    let name = value.type_name();
+    let missing = || Err(missing_method(name, method)).at(span);
+
+    let output = match value {
+        Value::Str(string) => match method {
+            "len" => Value::Int(string.len() as i64),
+            "trim" => Value::Str(string.trim().into()),
+            "split" => Value::Array(string.split(args.eat()?)),
+            _ => missing()?,
+        },
+
+        Value::Array(array) => match method {
+            "len" => Value::Int(array.len()),
+            "slice" => {
+                let start = args.expect("start")?;
+                let mut end = args.eat()?;
+                if end.is_none() {
+                    end = args.named("count")?.map(|c: i64| start + c);
+                }
+                Value::Array(array.slice(start, end).at(span)?)
+            }
+            "map" => Value::Array(array.map(ctx, args.expect("function")?)?),
+            "filter" => Value::Array(array.filter(ctx, args.expect("function")?)?),
+            "flatten" => Value::Array(array.flatten()),
+            "find" => array.find(args.expect("value")?).map_or(Value::None, Value::Int),
+            "join" => {
+                let sep = args.eat()?;
+                let last = args.named("last")?;
+                array.join(sep, last).at(span)?
+            }
+            "sorted" => Value::Array(array.sorted().at(span)?),
+            _ => missing()?,
+        },
+
+        Value::Dict(dict) => match method {
+            "len" => Value::Int(dict.len()),
+            "keys" => Value::Array(dict.keys()),
+            "values" => Value::Array(dict.values()),
+            "pairs" => Value::Array(dict.map(ctx, args.expect("function")?)?),
+            _ => missing()?,
+        },
+
+        Value::Func(func) => match method {
+            "with" => Value::Func(func.clone().with(args.take())),
+            _ => missing()?,
+        },
+
+        Value::Args(args) => match method {
+            "positional" => Value::Array(args.to_positional()),
+            "named" => Value::Dict(args.to_named()),
+            _ => missing()?,
+        },
+
+        _ => missing()?,
+    };
+
+    args.finish()?;
+    Ok(output)
+}
+
+/// Call a mutating method on a value.
+pub fn call_mut(
+    _: &mut Context,
+    value: &mut Value,
+    method: &str,
+    mut args: Args,
+    span: Span,
+) -> TypResult<()> {
+    let name = value.type_name();
+    let missing = || Err(missing_method(name, method)).at(span);
+
+    match value {
+        Value::Array(array) => match method {
+            "push" => array.push(args.expect("value")?),
+            "pop" => array.pop().at(span)?,
+            "insert" => {
+                array.insert(args.expect("index")?, args.expect("value")?).at(span)?
+            }
+            "remove" => array.remove(args.expect("index")?).at(span)?,
+            _ => missing()?,
+        },
+
+        Value::Dict(dict) => match method {
+            "remove" => dict.remove(args.expect("key")?).at(span)?,
+            _ => missing()?,
+        },
+
+        _ => missing()?,
+    }
+
+    args.finish()?;
+    Ok(())
+}
+
+/// Whether a specific method is mutating.
+pub fn is_mutating(method: &str) -> bool {
+    matches!(method, "push" | "pop" | "insert" | "remove")
+}
+
+/// The missing method error message.
+#[cold]
+fn missing_method(type_name: &str, method: &str) -> String {
+    format!("type {type_name} has no method `{method}`")
+}