// ── Pure LLVM IR code generation — zero-DOM, flat DFA model ───────────
//
// Every block is an LLVM IR label.  Every edge is a `br` instruction.
// Decisions become `br i1 %cond, label %yes, label %no`.
// Error handling becomes `br i1 %result, label %err, label %ok`.

(function () {
  "use strict";

  var CodeGen = {};

  // ── String pool ─────────────────────────────────────────────────────

  var _strPool = [];
  CodeGen.resetStringPool = function () { _strPool = []; };
  CodeGen.getStringPool = function () { return _strPool; };

  /**
   * Registers a string literal and returns its unique index.
   */
  CodeGen.allocString = function (s) {
    var idx = _strPool.indexOf(s);
    if (idx === -1) { idx = _strPool.length; _strPool.push(s); }
    return idx;
  };

  /**
   * Escapes a JS string for LLVM IR `c"..."` constant, and produces
   * the full `getelementptr` reference for use as a call argument.
   */
  CodeGen.llvmStringArg = function (str, idx) {
    var escaped = "";
    for (var i = 0; i < str.length; i++) {
      var ch = str.charCodeAt(i);
      if (ch === 0x22) escaped += "\\22";
      else if (ch === 0x5C) escaped += "\\5C";
      else if (ch === 0x0A) escaped += "\\0A";
      else if (ch === 0x0D) escaped += "\\0D";
      else if (ch === 0x09) escaped += "\\09";
      else if (ch < 0x20 || ch > 0x7E) {
        escaped += "\\" + ch.toString(16).toUpperCase().padStart(2, "0");
      } else {
        escaped += str[i];
      }
    }
    var byteLen = str.length + 1; // includes null terminator
    return "i8* getelementptr inbounds ([" + byteLen + " x i8], [" + byteLen + " x i8]* @.str." + idx + ", i32 0, i32 0)";
  };

  /**
   * Generates the LLVM IR global constant for a string pool entry.
   */
  CodeGen.stringGlobal = function (idx) {
    var str = _strPool[idx];
    var escaped = "", byteLen = 0;
    for (var i = 0; i < str.length; i++) {
      var ch = str.charCodeAt(i);
      byteLen++;
      if (ch === 0x22) escaped += "\\22";
      else if (ch === 0x5C) escaped += "\\5C";
      else if (ch === 0x0A) escaped += "\\0A";
      else if (ch === 0x0D) escaped += "\\0D";
      else if (ch === 0x09) escaped += "\\09";
      else if (ch < 0x20 || ch > 0x7E) {
        var h = ch.toString(16).toUpperCase();
        escaped += "\\" + (h.length === 1 ? "0" : "") + h;
      } else {
        escaped += str[i];
      }
    }
    byteLen++; // null terminator
    return "@.str." + idx + " = private unnamed_addr constant [" + byteLen + " x i8] c\"" + escaped + "\\00\"";
  };

  // ── Flat DFA emit ───────────────────────────────────────────────────

  CodeGen.emitFlat = function (entry) {
    var visited = new Set();
    var parts = [];

    function bb(block) { return "bb_" + block.id; }

    function emit(block) {
      if (visited.has(block)) {
        parts.push("  br label %" + bb(block) + "\n");
        return;
      }
      visited.add(block);
      parts.push("\n" + bb(block) + ":");

      var own = block.generateOwnCode();
      if (own) parts.push(own);

      var flow = block.wcNextFlow || block.nextFlow || [];
      var fc = "";
      if (typeof block.generateFlowCode === "function") {
        fc = block.generateFlowCode();
        // Replace bare label references with bb_ prefixed versions
        var replaced = "";
        var pos = 0, m;
        while ((m = /label\s+%([\w.]+)/g).lastIndex = pos, m = m.exec(fc)) {
          replaced += fc.slice(pos, m.index) + "label %bb_" + m[1];
          pos = m.index + m[0].length;
        }
        replaced += fc.slice(pos);
        fc = replaced;
      } else {
        for (var i = 0; i < flow.length; i++) {
          var t = flow[i].toElement;
          if (t) fc += "  br label %" + bb(t) + "\n";
        }
      }
      if (fc) parts.push("\n" + fc);

      for (var i = 0; i < flow.length; i++) {
        var t = flow[i].toElement;
        if (t) emit(t);
      }
    }

    emit(entry);
    return parts.join("");
  };

  // ── Full module assembly ────────────────────────────────────────────

  CodeGen.generateIRFile = function (entryBlock, declarations, globals, prologue) {
    var lines = ["; ModuleID = \"wisecode\"", "target triple = \"x86_64-pc-linux-gnu\"", ""];
    if (declarations) lines.push(declarations);
    if (globals) lines.push(globals);
    lines.push("");
    lines.push("define i32 @main() {");
    if (prologue) lines.push("entry:\n" + prologue + "\n  br label %bb_" + entryBlock.id);
    lines.push(CodeGen.emitFlat(entryBlock));
    lines.push("}");
    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;
  }
})();