1 files changed, 146 insertions, 0 deletions
diff --git a/src/Scope.php b/src/Scope.php
new file mode 100644
index 0000000..0da2724
--- /dev/null
+++ b/src/Scope.php
@@ -0,0 +1,146 @@
+<?php
+
+namespace kch42\ste;
+
+class Scope implements \ArrayAccess {
+	private $parent = NULL;
+	private $vars = array();
+	
+	private static function parse_name($name) {
+		$remain = $name;
+		$fields = array();
+		
+		while($remain !== "") {
+			$br_open = strpos($remain, '[');
+			if($br_open === false) {
+				$fields[] = $remain;
+				break;
+			}
+			
+			$br_close = strpos($remain, ']', $br_open);
+			if($br_close === false) {
+				throw new RuntimeError("Invalid varname \"$name\". Missing closing \"]\".");
+			}
+			
+			$fields[] = substr($remain, 0, $br_open);
+			
+			$field = substr($remain, $br_open+1, $br_close-$br_open-1);
+			$more = substr($remain, $br_close+1);
+			
+			if(strpos($field, '[') !== false) {
+				throw new RuntimeError("A variable field must not contain a '[' character.");
+			}
+			
+			if((strlen($more) > 0) && ($more[0] !== '[')) {
+				// TODO: better error message, not very non-programmer friendly...
+				throw new RuntimeError("A variable name must be of format name('[' name ']')*.");
+			}
+			
+			$remain = $field . $more;
+		}
+		
+		return $fields;
+	}
+	
+	private function &get_topvar_reference($name, $localonly) {
+		if(array_key_exists($name, $this->vars)) {
+			$ref = &$this->vars[$name];
+			return $ref;
+		}
+		
+		if((!$localonly) && ($this->parent !== NULL)) {
+			$ref = &$this->parent->get_topvar_reference($name, $localonly);
+			return $ref;
+		}
+
+		throw new VarNotInScope();
+	}
+	
+	public function &get_var_reference($name, $create_if_not_exist, $localonly=false) {
+		$nullref = NULL;
+		
+		$fields = self::parse_name($name);
+		if(count($fields) == 0) {
+			return $nullref; // TODO: or should we throw an exception here?
+		}
+		
+		$first = $fields[0];
+		
+		$ref = NULL;
+		try {
+			$ref = &$this->get_topvar_reference($first, $localonly);
+		} catch(VarNotInScope $e) {
+			if($create_if_not_exist) {
+				$this->vars[$first] = (count($fields) > 0) ? array() : "";
+				$ref = &$this->vars[$first];
+			} else {
+				return $nullref;
+			}
+		}
+		
+		for($i = 1; $i < count($fields); $i++) {
+			$field = $fields[$i];
+			
+			if(!is_array($ref)) {
+				return $nullref;
+			}
+			
+			if(!array_key_exists($field, $ref)) {
+				if(!$create_if_not_exist) {
+					return $nullref;
+				}
+				
+				if($i < count($fields) - 1) {
+					$ref[$field] = array();
+				} else {
+					$ref[$field] = "";
+				}
+			}
+			
+			$ref = &$ref[$field];
+		}
+		
+		return $ref;
+	}
+	
+	public function set_var_by_name($name, $val) {
+		$ref = &$this->get_var_reference($name, true);
+		$ref = $val;
+	}
+	
+	public function set_local_var($name, $val) {
+		$ref = &$this->get_var_reference($name, true, true);
+		$ref = $val;
+	}
+	
+	public function get_var_by_name($name) {
+		$ref = $this->get_var_reference($name, false);
+		return $ref === NULL ? "" : $ref;
+	}
+	
+	public function new_subscope() {
+		$o = new self();
+		$o->parent = $this;
+		return $o;
+	}
+	
+	/* implementing ArrayAccess */
+	
+	public function offsetSet($offset, $value) {
+		$this->set_var_by_name($offset, $value);
+	}
+	public function offsetGet($offset) {
+		return $this->get_var_by_name($offset);
+	}
+	public function offsetExists($offset) {
+		try {
+			$this->get_topvar_reference($offset);
+			return true;
+		} catch(VarNotInScope $e) {
+			return false;
+		}
+	}
+	public function offsetUnset($offset) {
+		unset($this->vars[$offset]);
+	}
+}