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// file : bpkg/help.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#include <bpkg/help>
#ifndef _WIN32
# include <unistd.h> // close()
#else
# include <io.h> // _close()
#endif
#include <chrono>
#include <thread> // this_thread::sleep_for()
#include <iostream>
#include <butl/process>
#include <butl/fdstream>
#include <bpkg/types>
#include <bpkg/utility>
#include <bpkg/diagnostics>
#include <bpkg/bpkg-options>
using namespace std;
using namespace butl;
namespace bpkg
{
struct pager
{
pager (const common_options& co, const string& name)
{
cstrings args;
string prompt;
bool up (co.pager_specified ()); // User's pager.
if (up)
{
if (co.pager ().empty ())
return; // No pager should be used.
args.push_back (co.pager ().c_str ());
}
else
{
// By default try less.
//
prompt = "-Ps" + name + " (press q to quit, h for help)";
args.push_back ("less");
args.push_back ("-R"); // Handle ANSI color.
args.push_back (prompt.c_str ());
}
// Add extra pager options.
//
for (const string& o: co.pager_option ())
args.push_back (o.c_str ());
args.push_back (nullptr);
if (verb >= 2)
print_process (args);
// Ignore errors and go without a pager unless the pager was specified
// by the user.
//
try
{
p_ = process (args.data (), -1); // Redirect child's stdin to a pipe.
// Wait a bit and see if the pager has exited before reading
// anything (e.g., because exec() couldn't find the program).
// If you know a cleaner way to handle this, let me know (no,
// a select()-based approach doesn't work; the pipe is buffered
// and therefore is always ready for writing).
//
this_thread::sleep_for (chrono::milliseconds (50));
bool r;
if (p_.try_wait (r))
{
#ifndef _WIN32
::close (p_.out_fd);
#else
_close (p_.out_fd);
#endif
if (up)
fail << "pager " << args[0] << " exited unexpectedly";
}
else
os_.open (p_.out_fd);
}
catch (const process_error& e)
{
// Ignore unless it was a user-specified pager.
//
if (up)
error << "unable to execute " << args[0] << ": " << e.what ();
if (e.child ())
exit (1);
if (up)
throw failed ();
}
}
std::ostream&
stream ()
{
return os_.is_open () ? os_ : std::cout;
}
bool
wait ()
{
os_.close ();
return p_.wait ();
}
~pager () {wait ();}
private:
process p_;
ofdstream os_;
};
int
help (const help_options& o, const string& t, usage_function* usage)
{
if (usage == nullptr) // Not a command.
{
if (t.empty ()) // General help.
usage = &print_bpkg_usage;
else if (t == "common-options") // Help topics.
usage = &print_bpkg_common_options_long_usage;
else
fail << "unknown bpkg command/help topic '" << t << "'" <<
info << "run 'bpkg help' for more information";
}
pager p (o, "bpkg " + (t.empty () ? "help" : t));
usage (p.stream (), cli::usage_para::none);
// If the pager failed, assume it has issued some diagnostics.
//
return p.wait () ? 0 : 1;
}
}
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