Refactor P4Compiler to P4Parser

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

Sources/P4Parser/Parsers/Program.swift

@@ -0,0 +1,72 @@
+// p4rse, Copyright 2026, Will Hawkins
+//
+// This file is part of p4rse.
+//
+// This file is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
+import Common
+import SwiftTreeSitter
+
+extension CST.Program: Parsable {
+  public typealias C = CST.Program
+  public static func Parse(
+    node: Node, withContext context: CSTCompilerContext
+  ) -> Common.Result<CST.Program> {
+
+    var statements: [CST.Statement] = Array()
+
+    var errors: (any Errorable)? = .none
+
+    // Try to parse all top-level declarations.
+    node.enumerateNamedChildren { (declaration_node: Node) in
+      let declaration_parsers: [String: ParsableStatement.Type] = [
+        "declaration": CST.Declaration.self,
+        "instantiation": CST.Instantiation.self,
+      ]
+
+      if let parser = declaration_parsers[declaration_node.nodeType!] {
+        let r = parser.ParseStatement(node: declaration_node, withContext: context)
+        switch r {
+        case .Ok(let compiled):
+          statements.append(compiled)
+        case .Error(let e):
+          errors =
+            if let errors = errors {
+              errors.append(error: e)
+            } else {
+              e
+            }
+
+        }
+      } else {
+        let e = ErrorWithLocation(
+          sourceLocation: declaration_node.toSourceLocation(),
+          withError:
+            "\(declaration_node.nodeType!) cannot be at a P4 program top level")
+        errors =
+          if let errors = errors {
+            errors.append(error: e)
+          } else {
+            e
+          }
+      }
+    }
+
+    if let errors = errors {
+      return .Error(errors)
+    }
+    return Result.Ok(CST.Program(CST.Statements(statements)))
+
+  }
+}