// ── Pure C code generation — no DOM dependencies ─────────────────────────
//
// These functions operate on generic block objects with the interface:
//   { generateOwnCode(): string,
//     generateCode(visited: Set): string,
//     wcNextFlow?: [{ toElement: block }],
//     nextFlow?: [{ toElement: block }] }
//
// Browser DOM blocks use wcNextFlow; test/mock blocks use nextFlow.
// Decision blocks must expose isDecision = true.

(function () {
  "use strict";

  var CodeGen = {};

  /**
   * Collects all blocks reachable from the given roots via nextFlow,
   * excluding the interior of decision blocks (they handle their own
   * branching).  Returns a Set of block references.
   * @param {Array} roots
   * @param {function(block): boolean} [isDecision]
   * @returns {Set}
   */
  CodeGen.branchDescendants = function (roots, isDecision) {
    isDecision =
      isDecision ||
      function (b) {
        return b.isDecision;
      };
    var d = new Set(),
      q = roots.slice();
    for (var i = 0; i < q.length; i++) {
      var el = q[i];
      if (d.has(el)) continue;
      d.add(el);
      if (isDecision(el)) continue;
      var flow = el.wcNextFlow || el.nextFlow || [];
      for (var j = 0; j < flow.length; j++) {
        var target = flow[j].toElement;
        if (target && !d.has(target)) q.push(target);
      }
    }
    return d;
  };

  /**
   * Emits C code for a branch by walking from root blocks, stopping at
   * blocks in the stop set and at decision boundaries.  Each visited block
   * is added to the visited set to prevent double-emission.
   * @param {Array} roots
   * @param {Set} stop  blocks to exclude (shared between branches)
   * @param {Set} visited  blocks already emitted
   * @param {function(block): boolean} [isDecision]
   * @returns {string}
   */
  CodeGen.emitBranch = function (roots, stop, visited, isDecision) {
    isDecision =
      isDecision ||
      function (b) {
        return b.isDecision;
      };
    var v = new Set(visited);
    var parts = [];

    function walk(el) {
      if (v.has(el) || (stop && stop.has(el))) return;
      v.add(el);
      if (isDecision(el)) {
        parts.push(el.generateCode(v));
      } else {
        parts.push(el.generateOwnCode());
        var flow = el.wcNextFlow || el.nextFlow || [];
        for (var j = 0; j < flow.length; j++) {
          walk(flow[j].toElement);
        }
      }
    }

    for (var i = 0; i < roots.length; i++) walk(roots[i]);
    return parts.join("");
  };

  /**
   * Generates the error-path branch for a proc call: computes shared blocks
   * between error and success paths, emits error-exclusive code inside `if`,
   * then success-exclusive and shared code after it (no else).
   * @param {string} ifHeader  e.g. 'if (func() != 0)' or 'if ((r=f()) != 0)'
   * @param {Array} errTargets  root blocks reachable from the error hook
   * @param {Array} okTargets   root blocks reachable from the success hook
   * @param {function(block): boolean} [isDecision]
   * @returns {string}
   */
  CodeGen.generateCallWithError = function (
    ifHeader,
    errTargets,
    okTargets,
    isDecision
  ) {
    var errAll = CodeGen.branchDescendants(errTargets, isDecision);
    var okAll = CodeGen.branchDescendants(okTargets, isDecision);
    var shared = new Set();
    errAll.forEach(function (b) {
      if (okAll.has(b)) shared.add(b);
    });

    var errCode = CodeGen.emitBranch(errTargets, shared, new Set(), isDecision);
    var okCode = CodeGen.emitBranch(okTargets, shared, new Set(), isDecision);
    var sharedCode = CodeGen.emitBranch(
      Array.from(shared),
      new Set(),
      new Set(),
      isDecision
    );

    var out = ifHeader + " {\n" + errCode + "}\n";
    if (okCode) out += okCode;
    if (sharedCode) out += sharedCode;
    return out;
  };

  /**
   * Assembles a complete C source file from a program's entry block,
   * include directives, and variable declarations.
   * @param {Object} entryBlock  the first block in the flow (e.g. START)
   * @param {string[]} includes  #include directives
   * @param {string} declarations  variable declarations (already indented)
   * @returns {string}
   */
  CodeGen.generateCFile = function (entryBlock, includes, declarations) {
    var lines = ["// --- WiseCode\u00ae ---"];
    for (var i = 0; i < includes.length; i++) lines.push(includes[i]);
    lines.push("");
    lines.push("int main() {");
    if (declarations) lines.push(declarations);
    var body = entryBlock.generateCode(new Set());
    lines.push(body);
    lines.push("}");
    lines.push("// --- END ---");
    return lines.join("\n");
  };

  // ── Export ──────────────────────────────────────────────────────────
  if (typeof module !== "undefined" && module.exports) {
    module.exports = CodeGen;
  }
  if (typeof window !== "undefined") {
    window.CodeGen = CodeGen;
  }
})();