text: // Copyright (c) 2013 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include <algorithm>
  #include <iostream>
  
  #include "tools/gn/args.h"
  #include "tools/gn/commands.h"
  #include "tools/gn/err.h"
  #include "tools/gn/functions.h"
  #include "tools/gn/input_conversion.h"
  #include "tools/gn/label_pattern.h"
  #include "tools/gn/setup.h"
  #include "tools/gn/standard_out.h"
  #include "tools/gn/substitution_writer.h"
  #include "tools/gn/variables.h"
  
  namespace commands {
  
  namespace {
  
  void PrintToplevelHelp() {
    OutputString("Commands (type \"gn help <command>\" for more details):\n");
    for (const auto& cmd : commands::GetCommands())
      PrintShortHelp(cmd.second.help_short);
  
    OutputString(
        "\n"
        "Common switches:\n");
    PrintShortHelp(
        "--args: Specifies build arguments overrides. "
        "See \"gn help buildargs\".");
    PrintShortHelp(
        "--[no]color: Forces colored output on or off (rather than autodetect).");
    PrintShortHelp(
        "--dotfile: Specifies an alternate .gn file. See \"gn help dotfile\".");
    PrintShortHelp(
        "--no-exec: Skips exec_script calls (for performance testing).");
    PrintShortHelp(
        "-q: Quiet mode, don't print anything on success.");
    PrintShortHelp(
        "--root: Specifies source root (overrides .gn file).");
    PrintShortHelp(
        "--time: Outputs a summary of how long everything took.");
    PrintShortHelp(
        "--tracelog: Writes a Chrome-compatible trace log to the given file.");
    PrintShortHelp(
        "-v: Verbose mode, print lots of logging.");
    PrintShortHelp(
        "--version: Print the GN binary's version and exit.");
  
    // Target declarations.
    OutputString("\nTarget declarations (type \"gn help <function>\" for more "
                 "details):\n");
    for (const auto& func : functions::GetFunctions()) {
      if (func.second.is_target)
        PrintShortHelp(func.second.help_short);
    }
  
    // Functions.
    OutputString("\nBuildfile functions (type \"gn help <function>\" for more "
                 "details):\n");
    for (const auto& func : functions::GetFunctions()) {
      if (!func.second.is_target)
        PrintShortHelp(func.second.help_short);
    }
  
    // Built-in variables.
    OutputString("\nBuilt-in predefined variables (type \"gn help <variable>\" "
                 "for more details):\n");
    for (const auto& builtin : variables::GetBuiltinVariables())
      PrintShortHelp(builtin.second.help_short);
  
    // Target variables.
    OutputString("\nVariables you set in targets (type \"gn help <variable>\" "
                 "for more details):\n");
    for (const auto& target : variables::GetTargetVariables())
      PrintShortHelp(target.second.help_short);
  
    OutputString("\nOther help topics:\n");
    PrintShortHelp("buildargs: How build arguments work.");
    PrintShortHelp("dotfile: Info about the toplevel .gn file.");
    PrintShortHelp("label_pattern: Matching more than one label.");
    PrintShortHelp(
        "input_conversion: Processing input from exec_script and read_file.");
    PrintShortHelp("source_expansion: Map sources to outputs for scripts.");
  }
  
  }  // namespace
  
  const char kHelp[] = "help";
  const char kHelp_HelpShort[] =
      "help: Does what you think.";
  const char kHelp_Help[] =
      "gn help <anything>\n"
      "  Yo dawg, I heard you like help on your help so I put help on the help\n"
      "  in the help.\n";
  
  int RunHelp(const std::vector<std::string>& args) {
    if (args.size() == 0) {
      PrintToplevelHelp();
      return 0;
    }
  
    // Check commands.
    const commands::CommandInfoMap& command_map = commands::GetCommands();
    commands::CommandInfoMap::const_iterator found_command =
        command_map.find(args[0]);
    if (found_command != command_map.end()) {
      PrintLongHelp(found_command->second.help);
      return 0;
    }
  
    // Check functions.
    const functions::FunctionInfoMap& function_map = functions::GetFunctions();
    functions::FunctionInfoMap::const_iterator found_function =
        function_map.find(args[0]);
    if (found_function != function_map.end()) {
      PrintLongHelp(found_function->second.help);
      return 0;
    }
  
    // Builtin variables.
    const variables::VariableInfoMap& builtin_vars =
        variables::GetBuiltinVariables();
    variables::VariableInfoMap::const_iterator found_builtin_var =
        builtin_vars.find(args[0]);
    if (found_builtin_var != builtin_vars.end()) {
      PrintLongHelp(found_builtin_var->second.help);
      return 0;
    }
  
    // Target variables.
    const variables::VariableInfoMap& target_vars =
        variables::GetTargetVariables();
    variables::VariableInfoMap::const_iterator found_target_var =
        target_vars.find(args[0]);
    if (found_target_var != target_vars.end()) {
      PrintLongHelp(found_target_var->second.help);
      return 0;
    }
  
    // Random other topics.
    if (args[0] == "buildargs") {
      PrintLongHelp(kBuildArgs_Help);
      return 0;
    }
    if (args[0] == "dotfile") {
      PrintLongHelp(kDotfile_Help);
      return 0;
    }
    if (args[0] == "input_conversion") {
      PrintLongHelp(kInputConversion_Help);
      return 0;
    }
    if (args[0] == "label_pattern") {
      PrintLongHelp(kLabelPattern_Help);
      return 0;
    }
    if (args[0] == "source_expansion") {
      PrintLongHelp(kSourceExpansion_Help);
      return 0;
    }
  
    // No help on this.
    Err(Location(), "No help on \"" + args[0] + "\".").PrintToStdout();
    RunHelp(std::vector<std::string>());
    return 1;
  }
  
  }  // namespace commands
  