1 files changed, 164 insertions, 0 deletions
diff --git a/lib/xixanta/src/node.rs b/lib/xixanta/src/node.rs
new file mode 100644
index 0000000..18a5402
--- /dev/null
+++ b/lib/xixanta/src/node.rs
@@ -0,0 +1,164 @@
+use std::fmt;
+use std::ops::Range;
+
+/// A Positioned String. That is, a String which also has information on the
+/// line number and the column range.
+#[derive(Debug, Default, Clone, PartialEq)]
+pub struct PString {
+    /// The actual value.
+    pub value: String,
+
+    /// Line number where it has been found.
+    pub line: usize,
+
+    /// The column range where it has been found.
+    pub range: Range<usize>,
+}
+
+impl PString {
+    /// Returns true if the string has either an empty value or an empty range.
+    pub fn is_empty(&self) -> bool {
+        self.value.is_empty() || self.range.is_empty()
+    }
+
+    /// Returns an empty tuple if the string contains a valid identifier, or a
+    /// String containing the error otherwise. If `allow_scoped` is set to true,
+    /// then identifiers with the "::" operator in it will be considered valid.
+    pub fn is_valid_identifier(&self, allow_scoped: bool) -> Result<(), String> {
+        if self.value.trim().is_empty() {
+            return Err(String::from("empty identifier"));
+        }
+
+        // You cannot assign into a name which is reserved.
+        if matches!(self.value.to_lowercase().as_str(), "x" | "y" | "a") {
+            return Err(format!("cannot use reserved name '{}'", self.value));
+        }
+
+        // You cannot assign into scoped names: declare them into their
+        // respective scopes instead.
+        if !allow_scoped && self.value.contains("::") {
+            return Err(format!(
+                "the name '{}' is scoped: do not declare things this way",
+                self.value
+            ));
+        }
+
+        // Let's gather info from the variable name which is relevant to later
+        // checks.
+        let mut alpha_seen = false;
+        let mut valid_hex = matches!(self.value.len(), 1..=4);
+        for c in self.value.to_lowercase().chars() {
+            if c == '_' {
+                valid_hex = false;
+            } else if c.is_alphabetic() {
+                alpha_seen = true;
+                if c > 'f' && c <= 'z' {
+                    valid_hex = false;
+                }
+            }
+        }
+
+        // We need at least one alphabetic character. Otherwise it might be
+        // confusing with numbers.
+        if !alpha_seen {
+            return Err(format!(
+                "name '{}' requires at least one alphabetic character",
+                self.value
+            ));
+        }
+
+        // To avoid problems down the line, you cannot assign into names which
+        // are proper hexadecimal values.
+        if valid_hex {
+            return Err(format!(
+                "cannot use names which are valid hexadecimal values such as '{}'",
+                self.value
+            ));
+        }
+
+        Ok(())
+    }
+}
+
+/// The PNode type.
+#[derive(Debug, Clone, PartialEq)]
+pub enum NodeType {
+    /// A general/abstract value. This can either be a variable, or a macro call
+    /// with no arguments. This is, thus, to be determined by the assembler
+    /// after a proper context has been set.
+    Value,
+
+    /// An instruction. The value of the PNode has the instruction mnemonic. The
+    /// left node is the "left arm", which is whatever is left of the comma from
+    /// expressions like "lda Left, x", or an Indirection on indirect addressing
+    /// mode (e.g. "lda (Indirect, x)"). The righ node contains the "right arm",
+    /// which basically contains the index on an indexed addressing mode.
+    Instruction,
+
+    /// An Indirection node, which might have two arms (e.g. "lda (Left,
+    /// Right)"), or just a left one (e.g. "lda (Left), y")
+    Indirection,
+
+    /// An assignment holds the name of the variable on the `value` and the
+    /// actual expression that initializes it on the `left`. The rest is None.
+    Assignment,
+
+    /// A control statement (e.g. ".proc foo"). The `value` string contains the
+    /// name of the function, the `left` an optional identifier (e.g. the "foo"
+    /// on ".proc foo"), and the `args` contain any possible arguments that have
+    /// been passed to this control statement.
+    Control,
+
+    /// A literal expression, that is, something that starts with '#', '%' or
+    /// '$'. The `left` node contains the inner expression.
+    Literal,
+
+    /// A label statement, which only sets the `value`, the name of the label.
+    Label,
+
+    /// A macro call. Note that a Value might also encode this, but when a Call
+    /// has been detected, then there is no doubt on it.
+    Call,
+}
+
+impl fmt::Display for NodeType {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            NodeType::Value => write!(f, "value"),
+            NodeType::Instruction => write!(f, "instruction"),
+            NodeType::Indirection => write!(f, "indirection"),
+            NodeType::Assignment => write!(f, "assignment"),
+            NodeType::Control => write!(f, "control function"),
+            NodeType::Literal => write!(f, "literal"),
+            NodeType::Label => write!(f, "label"),
+            NodeType::Call => write!(f, "call"),
+        }
+    }
+}
+
+/// A Position Node. This is a node on a binary tree which holds a PString as a
+/// value. The node type determines the actual representation of the value and
+/// both childs (see the `NodeType` enum). Moreover, out of convenience, a node
+/// also holds an optional list of arguments, which simplifies arrangements such
+/// as the `Call` or the `Control` node types.
+#[derive(Debug, Clone)]
+pub struct PNode {
+    /// The type of the PNode.
+    pub node_type: NodeType,
+
+    /// A Positioned String acting as the value. Check with the `NodeType`
+    /// documentation to check when it makes sense to use it.
+    pub value: PString,
+
+    /// The left child of the node. Check with the `NodeType` documentation to
+    /// check when it makes sense to use it.
+    pub left: Option<Box<PNode>>,
+
+    /// The right child of the node. Check with the `NodeType` documentation to
+    /// check when it makes sense to use it.
+    pub right: Option<Box<PNode>>,
+
+    /// Convenience list used by some node types in order to express a list of
+    /// optional arguments.
+    pub args: Option<Vec<PNode>>,
+}