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|
use crate::assembler::Bundle;
use crate::errors::{ContextError, ContextErrorReason};
use crate::node::{ControlType, NodeType, PNode, PString};
use crate::opcodes::CONTROL_FUNCTIONS;
use std::collections::HashMap;
// The name of the global context as used internally..
const GLOBAL_CONTEXT: &str = "Global";
/// Context holds information about the different scopes being defined, the
/// current scope, and has a map of all the variables defined for each scope.
#[derive(Debug)]
pub struct Context {
stack: Vec<String>,
map: HashMap<String, HashMap<String, Bundle>>,
}
impl Context {
/// Returns a new empty context.
pub fn new() -> Self {
Context {
stack: vec![],
map: HashMap::from([(String::from(GLOBAL_CONTEXT), HashMap::new())]),
}
}
/// Returns the value of the variable represented by the given `id`. Note
/// that this `id` can be scoped or not, and this function will try to pick
/// the variable from the right scope.
pub fn get_variable(&self, id: &PString) -> Result<Bundle, ContextError> {
// First of all, figure out the name of the scope and the real name of
// the variable. If this was not scoped at all (None case when trying to
// rsplit by the "::" operator), then we assume it's a global variable.
let (scope_name, var_name) = match id.value.rsplit_once("::") {
Some((scope, name)) => (scope, name),
None => (self.name(), id.value.as_str()),
};
// And with that, the only thing left is to find the scope and the
// variable in it.
match self.map.get(scope_name) {
Some(scope) => match scope.get(var_name) {
Some(var) => Ok(var.clone()),
None => Err(ContextError {
message: format!(
"could not find variable '{}' in {}",
var_name,
self.to_human_with(scope_name)
),
line: id.line,
reason: ContextErrorReason::UnknownVariable,
}),
},
None => Err(ContextError {
message: format!("did not find scope '{}'", scope_name),
line: id.line,
reason: ContextErrorReason::BadScope,
}),
}
}
/// Sets a value for a variable defined in the assignment `node`. If
/// `overwrite` is set to true, then this value will be set even if the
/// variable already existed, otherwise it will return a ContextError
pub fn set_variable(
&mut self,
id: &PString,
bundle: &Bundle,
overwrite: bool,
) -> Result<(), ContextError> {
let scope_name = self.name().to_string();
let scope = self.map.get_mut(&scope_name).unwrap();
match scope.get_mut(&id.value) {
Some(sc) => {
if !overwrite {
return Err(ContextError {
message: format!(
"'{}' already defined in {}: you cannot re-assign variables",
id.value,
self.to_human()
),
line: id.line,
reason: ContextErrorReason::Redefinition,
});
}
*sc = bundle.clone();
}
None => {
scope.insert(id.value.clone(), bundle.to_owned());
}
}
Ok(())
}
/// Change the current context given a `node`. Returns a tuple which states:
/// 0. Whether the context has changed.
/// 1. Whether a caller can bundle nodes safely.
pub fn change_context(&mut self, node: &PNode) -> Result<(bool, bool), ContextError> {
// The parser already guarantees that the control node is
// from a function that we already know, so calling `unwrap`
// is not dangerous.
let control = CONTROL_FUNCTIONS
.get(&node.value.value.to_lowercase())
.unwrap();
// If the control function does not touch the context, leave early.
if !control.touches_context {
return Ok((false, true));
}
// And push/pop the context depending on the control being used.
match node.node_type {
NodeType::Control(ControlType::StartMacro) => {
self.context_push(&node.left.clone().unwrap());
Ok((true, false))
}
NodeType::Control(ControlType::StartProc)
| NodeType::Control(ControlType::StartScope) => {
self.context_push(&node.left.clone().unwrap());
Ok((true, true))
}
NodeType::Control(ControlType::EndMacro)
| NodeType::Control(ControlType::EndProc)
| NodeType::Control(ControlType::EndScope) => {
self.context_pop(&node.value)?;
Ok((true, true))
}
_ => Ok((false, true)),
}
}
pub fn force_context_switch(&mut self, name: &String) {
self.stack.push(name.to_owned());
}
pub fn force_context_pop(&mut self) {
if !self.stack.is_empty() {
self.stack.truncate(self.stack.len() - 1);
}
}
// Pushes a new context given a `node`, which holds the identifier of the
// new scope.
fn context_push(&mut self, id: &PNode) {
let name = match self.stack.last() {
Some(n) => format!("{}::{}", n, id.value.value),
None => id.value.value.clone(),
};
// Actually push the name to the stack and initialize it on the variable
// map.
self.stack.push(name.clone());
self.map.entry(name).or_default();
}
// Pops out the latest context that was pushed.
fn context_pop(&mut self, id: &PString) -> Result<(), ContextError> {
if self.stack.is_empty() {
return Err(ContextError {
message: format!("missplaced '{}' statement", id.value),
reason: ContextErrorReason::BadScope,
line: id.line,
});
}
self.stack.truncate(self.stack.len() - 1);
Ok(())
}
// Returns the name of the current context.
pub fn name(&self) -> &str {
match self.stack.last() {
Some(name) => name,
None => GLOBAL_CONTEXT,
}
}
// Returns a human-readable string representing the current context.
fn to_human(&self) -> String {
match self.stack.last() {
Some(n) => format!("'{}'", n),
None => "the global scope".to_string(),
}
}
// Returns a human-readable string representing the given context.
fn to_human_with(&self, name: &str) -> String {
if name == GLOBAL_CONTEXT {
"the global scope".to_string()
} else {
format!("'{}'", name)
}
}
}
impl Default for Context {
fn default() -> Self {
Self::new()
}
}
|
