#include "JetCodegen.h"
#include <stdexcept>

namespace jetc {

   std::string Codegen::ind(int indent) {
      return std::string(indent * 3, ' ');
   }

   std::string Codegen::cstr(const std::string &raw) {
      std::string r;
      r.reserve(raw.size() + 8);
      r += '"';
      for (unsigned char c : raw) {
         switch (c) {
          case '\\': r += "\\\\"; break;
          case '"':  r += "\\\""; break;
          case '\n': r += "\\n";  break;
          case '\r': r += "\\r";  break;
          case '\t': r += "\\t";  break;
          default:
             if (c < 0x20) {
                char buf[8];
                snprintf(buf, sizeof(buf), "\\x%02x\" \"", c);
                r += buf;
             } else {
                r += (char)c;
             }
         }
      }
      r += '"';
      return r;
   }

   const char *Codegen::staticTypeOp(const std::string &type, const char *rc) {
      // type is known at compile time (a literal attribute value, not a
      // runtime expression) so the comparison operator is picked once here
      // instead of being re-checked against six string constants on every
      // request the way Tag::__if/__while do it at runtime.
      static thread_local std::string expr;
      if (type == "eq") expr = std::string(rc) + " == 0";
      else if (type == "ne") expr = std::string(rc) + " != 0";
      else if (type == "lt") expr = std::string(rc) + " == -1";
      else if (type == "le") expr = std::string(rc) + " != 1";
      else if (type == "gt") expr = std::string(rc) + " == 1";
      else if (type == "ge") expr = std::string(rc) + " != -1";
      else throw std::runtime_error("jetc: type=\"" + type + "\" is not one of eq/ne/lt/le/gt/ge "
              "(and jetc only supports a literal type= value - use expr= for a dynamic comparison).");
      return expr.c_str();
   }

   void Codegen::emitBody(const std::vector<NodePtr> &nodes, int indent, std::ostringstream &target) {
      for (auto &n : nodes) emitNode(n, indent, target);
   }

   void Codegen::emitNode(const NodePtr &n, int indent, std::ostringstream &target) {
      std::string I = ind(indent);
      switch (n->kind) {

       case NodeKind::TEXT: {
          if (n->text.empty()) break;
          target << I << "out << " << cstr(n->text) << ";\n";
          break;
       }

       case NodeKind::VAR: {
          target << I << "{ coreutils::ZString v(" << cstr(n->varText) << "); out << scope.getVariable(v, true); }\n";
          break;
       }

       case NodeKind::SET: {
          std::string k = id("set_");
          target << I << "{\n";
          target << I << "   scope.keywords[\"" << k << "name\"] = " << cstr(n->setName) << ";\n";
          target << I << "   scope.keywords[\"" << k << "scope\"] = " << cstr(n->setScope) << ";\n";
          target << I << "   coreutils::MString val;\n";
          if (n->setHasExpr) {
             target << I << "   scope.keywords[\"" << k << "expr\"] = " << cstr(n->setExpr) << ";\n";
             target << I << "   val = jet::Operand(scope.keywords[\"" << k << "expr\"], scope).string;\n";
          } else {
             target << I << "   scope.keywords[\"" << k << "value\"] = " << cstr(n->setHasValue ? n->setValue : std::string()) << ";\n";
             target << I << "   val = scope.resolveKeyword(\"" << k << "value\");\n";
          }
          target << I << "   scope.assignVariable(scope.resolveKeyword(\"" << k << "name\"), val, scope.resolveKeyword(\"" << k << "scope\"));\n";
          target << I << "}\n";
          break;
       }

       case NodeKind::IF: {
          std::string k = id("if_");
          target << I << "{\n";
          target << I << "   bool cond;\n";
          if (n->cond.mode == CondMode::EXPR) {
             target << I << "   scope.keywords[\"" << k << "expr\"] = " << cstr(n->cond.expr) << ";\n";
             target << I << "   cond = jet::Operand(scope.keywords[\"" << k << "expr\"], scope).boolean;\n";
          } else {
             target << I << "   scope.keywords[\"" << k << "value1\"] = " << cstr(n->cond.value1) << ";\n";
             target << I << "   scope.keywords[\"" << k << "value2\"] = " << cstr(n->cond.value2) << ";\n";
             target << I << "   int rc = scope.resolveKeyword(\"" << k << "value1\").compare(scope.resolveKeyword(\"" << k << "value2\"));\n";
             target << I << "   cond = (" << staticTypeOp(n->cond.type, "rc") << ");\n";
          }
          target << I << "   if (cond) {\n";
          emitBody(n->thenBody, indent + 2, target);
          if (n->hasElse) {
             target << I << "   } else {\n";
             emitBody(n->elseBody, indent + 2, target);
          }
          target << I << "   }\n";
          target << I << "}\n";
          break;
       }

       case NodeKind::FOR: {
          std::string k = id("for_");
          target << I << "{\n";
          target << I << "   scope.keywords[\"" << k << "start\"] = " << cstr(n->forHasStart ? n->forStart : std::string("0")) << ";\n";
          target << I << "   scope.keywords[\"" << k << "end\"] = " << cstr(n->forEnd) << ";\n";
          target << I << "   scope.keywords[\"" << k << "step\"] = " << cstr(n->forStep) << ";\n";
          target << I << "   double ix = scope.resolveKeyword(\"" << k << "start\").asDouble();\n";
          if (n->forHasName) {
             target << I << "   scope.keywords[\"" << k << "name\"] = " << cstr(n->forName) << ";\n";
             target << I << "   scope.keywords[\"" << k << "scope\"] = " << cstr(n->forScope) << ";\n";
          }
          target << I << "   for (; ix <= scope.resolveKeyword(\"" << k << "end\").asDouble(); ix += scope.resolveKeyword(\"" << k << "step\").asDouble()) {\n";
          if (n->forHasName) {
             target << I << "      coreutils::MString nameSel = scope.resolveKeyword(\"" << k << "name\");\n";
             target << I << "      coreutils::MString scopeSel = scope.resolveKeyword(\"" << k << "scope\");\n";
             target << I << "      if ((scopeSel == \"\") || (scopeSel == \"global\")) global.variables[nameSel] = ix;\n";
             target << I << "      else if (scopeSel == \"local\") scope.local->variables[nameSel] = ix;\n";
             target << I << "      else if (scopeSel == \"parent\") scope.parent->local->variables[nameSel] = ix;\n";
             target << I << "      else throw coreutils::Exception(\"scope value is not valid.\");\n";
          }
          emitBody(n->body, indent + 2, target);
          target << I << "   }\n";
          target << I << "}\n";
          break;
       }

       case NodeKind::WHILE: {
          std::string k = id("while_");
          target << I << "{\n";
          target << I << "   bool cond;\n";
          if (n->cond.mode == CondMode::EXPR) {
             target << I << "   scope.keywords[\"" << k << "expr\"] = " << cstr(n->cond.expr) << ";\n";
             target << I << "   coreutils::MString exprSaved = scope.keywords[\"" << k << "expr\"];\n";
             target << I << "   cond = jet::Operand(scope.keywords[\"" << k << "expr\"], scope).boolean;\n";
             target << I << "   while (cond) {\n";
             emitBody(n->body, indent + 2, target);
             target << I << "      scope.keywords[\"" << k << "expr\"].reset();\n";
             target << I << "      scope.keywords[\"" << k << "expr\"] = exprSaved;\n";
             target << I << "      cond = jet::Operand(scope.keywords[\"" << k << "expr\"], scope).boolean;\n";
             target << I << "   }\n";
          } else {
             target << I << "   scope.keywords[\"" << k << "value1\"] = " << cstr(n->cond.value1) << ";\n";
             target << I << "   scope.keywords[\"" << k << "value2\"] = " << cstr(n->cond.value2) << ";\n";
             target << I << "   int rc = scope.resolveKeyword(\"" << k << "value1\").compare(scope.resolveKeyword(\"" << k << "value2\"));\n";
             target << I << "   cond = (" << staticTypeOp(n->cond.type, "rc") << ");\n";
             target << I << "   while (cond) {\n";
             emitBody(n->body, indent + 2, target);
             target << I << "      int rc2 = scope.resolveKeyword(\"" << k << "value1\").compare(scope.resolveKeyword(\"" << k << "value2\"));\n";
             target << I << "      cond = (" << staticTypeOp(n->cond.type, "rc2") << ");\n";
             target << I << "   }\n";
          }
          target << I << "}\n";
          break;
       }

       case NodeKind::FALLBACK: {
          target << I << "{ coreutils::ZString span(" << cstr(n->rawSpan) << "); scope.interpretSpan(span, out); }\n";
          break;
       }

       case NodeKind::CONTAINER_SLOT: {
          // Reuses the interpreter's own <container> scope-walking logic
          // verbatim (see Tag::renderContainer) rather than re-deriving
          // it - this is exactly what the runtime's own <container>
          // dispatch does when it's reached via interpretSpan, just
          // without the text-scanning step to get there.
          target << I << "scope.renderContainer(out);\n";
          break;
       }

       case NodeKind::TAGDEF: {
          // Codegen can still fail for a node that parsed successfully -
          // e.g. an <if>/<while> whose type= isn't one of eq/ne/lt/le/gt/ge
          // (staticTypeOp's own check - real legacy content occasionally
          // has one of these sitting in a branch that's never actually
          // reached at runtime either, so there's nothing to "correctly"
          // compile). Parsing this definition's body already succeeded
          // (see parseTagDef's own try/catch for that stage) or this node
          // wouldn't exist as TAGDEF at all - so mirror that same
          // graceful-degradation approach here for the emit stage: try
          // building the compiled function into a throwaway stream first,
          // and only splice it into tagDefFuncs (and register the
          // compiledTags fast path) if that fully succeeds. A failure
          // here just means this one definition stays interpreted,
          // unchanged - zero risk to the rest of the file.
          std::string funcName = "jetc_tagdef_" + id("");
          std::ostringstream trial;
          bool compiledOk = true;
          try {
             trial << "static void " << funcName << "(jet::Tag &scope, coreutils::MString &out) {\n";
             emitBody(n->tagDefBody, 1, trial);
             trial << "}\n\n";
          } catch (const std::exception &) {
             compiledOk = false;
          }

          // Emitted in place, at this TAGDEF's original position in
          // program flow - matches exactly what FALLBACK would have
          // emitted for this same <tag name="X">...</tag> span, so
          // global.tags["x"] still gets populated as before (needed as a
          // correctness fallback: any invocation this compiler doesn't
          // itself recognize - e.g. reached through content this pass
          // never compiled - still resolves it exactly as it always has).
          target << I << "{ coreutils::ZString span(" << cstr(n->rawSpan) << "); scope.interpretSpan(span, out); }\n";
          if (compiledOk) {
             // The registration into compiledTags right after is the only
             // new behavior beyond the raw registration above - a pure
             // additive fast path __dotag checks first (see __dotag.cpp);
             // a miss there falls through to the now-unchanged interpreted
             // path, which is exactly what happens when compiledOk is
             // false here too.
             tagDefFuncs << trial.str();
             target << I << "global.compiledTags[coreutils::MString(" << cstr(n->tagDefName) << ")] = &" << funcName << ";\n";
          }
          break;
       }
      }
   }

   std::string Codegen::generate(const std::vector<NodePtr> &top, const std::string &sourceFileComment,
                                  bool sharedMode, const std::string &entrySymbol,
                                  const std::vector<ApiRoute> &apiRoutes, const std::string &apiSymbol) {
      out.str("");
      out.clear();
      tagDefFuncs.str("");
      tagDefFuncs.clear();

      out << "// " << sourceFileComment << "\n";
      out << "// Generated by jetc - DO NOT EDIT BY HAND.\n";
      out << "#include \"Global.h\"\n";
      out << "#include \"Tag.h\"\n";
      out << "#include \"Operand.h\"\n";
      out << "#include \"ZString.h\"\n";
      out << "#include \"MString.h\"\n";
      out << "#include \"Exception.h\"\n";
      out << "#include <iostream>\n\n";

      // The entry function's own text is built into a separate stream so
      // tagDefFuncs - populated as a SIDE EFFECT of the emitBody() call
      // below, since TAGDEF nodes append to it as they're encountered -
      // can be spliced in ahead of it. A compiled tag-definition function
      // never needs to be forward-declared for anything defined before it
      // in program order (nothing upstream calls it directly - see
      // __dotag.cpp's runtime lookup instead), so this ordering is purely
      // for readability, not a correctness requirement.
      std::ostringstream body;

      if (sharedMode) {
         if (!apiRoutes.empty()) {
            // A plain C struct, not any CoreUtils/JetCore type - this is the
            // one piece of the plugin ABI a host loader needs to know about
            // independent of the rest of this same-ABI C++ boundary.
            body << "struct JetApiRoute { const char *method; const char *path; };\n";
            body << "extern \"C\" const JetApiRoute *" << apiSymbol << "(int *count) {\n";
            body << "   static const JetApiRoute routes[] = {\n";
            for (auto &r : apiRoutes)
               body << "      { " << cstr(r.method) << ", " << cstr(r.path) << " },\n";
            body << "   };\n";
            body << "   *count = " << apiRoutes.size() << ";\n";
            body << "   return routes;\n";
            body << "}\n\n";
         }
         body << "extern \"C\" void " << entrySymbol << "(jet::Global &global, coreutils::MString &out) {\n";
         body << "   coreutils::ZString jetc_empty(\"\");\n";
         body << "   coreutils::MString jetc_scopeOut;\n";
         body << "   jet::Tag scope(jetc_empty, jetc_scopeOut, global, NULL, NULL);\n";
         emitBody(top, 1, body);
         body << "}\n";
         return out.str() + tagDefFuncs.str() + body.str();
      }

      body << "static void jetc_render(jet::Global &global, coreutils::MString &out) {\n";
      body << "   coreutils::ZString jetc_empty(\"\");\n";
      body << "   coreutils::MString jetc_scopeOut;\n";
      body << "   jet::Tag scope(jetc_empty, jetc_scopeOut, global, NULL, NULL);\n";
      emitBody(top, 1, body);
      body << "}\n\n";
      body << "int main(int argc, char **argv, char **envp) {\n";
      body << "   jet::Global global(envp);\n";
      body << "   coreutils::MString out;\n";
      body << "   try {\n";
      body << "      jetc_render(global, out);\n";
      body << "      global.outputHeaders();\n";
      body << "      std::cout << out;\n";
      body << "   } catch(coreutils::Exception e) {\n";
      body << "      std::cout << out;\n";
      body << "      std::cout << \"\\n----- Error: \" << e.text << std::endl;\n";
      body << "      return 1;\n";
      body << "   }\n";
      body << "   return 0;\n";
      body << "}\n";
      return out.str() + tagDefFuncs.str() + body.str();
   }

}