#include "cache.h"
#include "exec_cmd.h"
#include "quote.h"
#include "argv-array.h"

#if defined(RUNTIME_PREFIX)

#if defined(HAVE_NS_GET_EXECUTABLE_PATH)
#include <mach-o/dyld.h>
#endif

#if defined(HAVE_BSD_KERN_PROC_SYSCTL)
#include <sys/param.h>
#include <sys/types.h>
#include <sys/sysctl.h>
#endif

#endif /* RUNTIME_PREFIX */

#define MAX_ARGS 32

static const char *system_prefix(void);

#ifdef RUNTIME_PREFIX

/**
 * When using a runtime prefix, Git dynamically resolves paths relative to its
 * executable.
 *
 * The method for determining the path of the executable is highly
 * platform-specific.
 */

/**
 * Path to the current Git executable. Resolved on startup by
 * 'git_resolve_executable_dir'.
 */
static const char *executable_dirname;

static const char *system_prefix(void)
{
	static const char *prefix;

	assert(executable_dirname);
	assert(is_absolute_path(executable_dirname));

	if (!prefix &&
	    !(prefix = strip_path_suffix(executable_dirname, GIT_EXEC_PATH)) &&
	    !(prefix = strip_path_suffix(executable_dirname, BINDIR)) &&
	    !(prefix = strip_path_suffix(executable_dirname, "git"))) {
		prefix = PREFIX;
		trace_printf("RUNTIME_PREFIX requested, "
			     "but prefix computation failed.  "
			     "Using static fallback '%s'.\n",
			     prefix);
	}
	return prefix;
}

/*
 * Resolves the executable path from argv[0], only if it is absolute.
 *
 * Returns 0 on success, -1 on failure.
 */
static int git_get_exec_path_from_argv0(struct strbuf *buf, const char *argv0)
{
	const char *slash;

	if (!argv0 || !*argv0)
		return -1;

	slash = find_last_dir_sep(argv0);
	if (slash) {
		trace_printf("trace: resolved executable path from argv0: %s\n",
			     argv0);
		strbuf_add_absolute_path(buf, argv0);
		return 0;
	}
	return -1;
}

#ifdef PROCFS_EXECUTABLE_PATH
/*
 * Resolves the executable path by examining a procfs symlink.
 *
 * Returns 0 on success, -1 on failure.
 */
static int git_get_exec_path_procfs(struct strbuf *buf)
{
	if (strbuf_realpath(buf, PROCFS_EXECUTABLE_PATH, 0)) {
		trace_printf(
			"trace: resolved executable path from procfs: %s\n",
			buf->buf);
		return 0;
	}
	return -1;
}
#endif /* PROCFS_EXECUTABLE_PATH */

#ifdef HAVE_BSD_KERN_PROC_SYSCTL
/*
 * Resolves the executable path using KERN_PROC_PATHNAME BSD sysctl.
 *
 * Returns 0 on success, -1 on failure.
 */
static int git_get_exec_path_bsd_sysctl(struct strbuf *buf)
{
	int mib[4];
	char path[MAXPATHLEN];
	size_t cb = sizeof(path);

	mib[0] = CTL_KERN;
	mib[1] = KERN_PROC;
	mib[2] = KERN_PROC_PATHNAME;
	mib[3] = -1;
	if (!sysctl(mib, 4, path, &cb, NULL, 0)) {
		trace_printf(
			"trace: resolved executable path from sysctl: %s\n",
			path);
		strbuf_addstr(buf, path);
		return 0;
	}
	return -1;
}
#endif /* HAVE_BSD_KERN_PROC_SYSCTL */

#ifdef HAVE_NS_GET_EXECUTABLE_PATH
/*
 * Resolves the executable path by querying Darwin applicaton stack.
 *
 * Returns 0 on success, -1 on failure.
 */
static int git_get_exec_path_darwin(struct strbuf *buf)
{
	char path[PATH_MAX];
	uint32_t size = sizeof(path);
	if (!_NSGetExecutablePath(path, &size)) {
		trace_printf(
			"trace: resolved executable path from Darwin stack: %s\n",
			path);
		strbuf_addstr(buf, path);
		return 0;
	}
	return -1;
}
#endif /* HAVE_NS_GET_EXECUTABLE_PATH */

/*
 * Resolves the absolute path of the current executable.
 *
 * Returns 0 on success, -1 on failure.
 */
static int git_get_exec_path(struct strbuf *buf, const char *argv0)
{
	/*
	 * Identifying the executable path is operating system specific.
	 * Selectively employ all available methods in order of preference,
	 * preferring highly-available authoratative methods over
	 * selectively-available or non- authoratative methods.
	 *
	 * All cases fall back on resolving against argv[0] if there isn't a
	 * better functional method. However, note that argv[0] can be
	 * used-supplied on many operating sysetems, and is not authoratative
	 * in those cases.
	 *
	 * Each of these functions returns 0 on success, so evaluation will stop
	 * after the first successful method.
	 */
	if (
#ifdef HAVE_BSD_KERN_PROC_SYSCTL
		git_get_exec_path_bsd_sysctl(buf) &&
#endif /* HAVE_BSD_KERN_PROC_SYSCTL */

#ifdef HAVE_NS_GET_EXECUTABLE_PATH
		git_get_exec_path_darwin(buf) &&
#endif /* HAVE_NS_GET_EXECUTABLE_PATH */

#ifdef PROCFS_EXECUTABLE_PATH
		git_get_exec_path_procfs(buf) &&
#endif /* PROCFS_EXECUTABLE_PATH */

		git_get_exec_path_from_argv0(buf, argv0)) {
		return -1;
	}

	if (strbuf_normalize_path(buf)) {
		trace_printf("trace: could not normalize path: %s\n", buf->buf);
		return -1;
	}

	return 0;
}

void git_resolve_executable_dir(const char *argv0)
{
	struct strbuf buf = STRBUF_INIT;
	char *resolved;
	const char *slash;

	if (git_get_exec_path(&buf, argv0)) {
		trace_printf(
			"trace: could not determine executable path from: %s\n",
			argv0);
		strbuf_release(&buf);
		return;
	}

	resolved = strbuf_detach(&buf, NULL);
	slash = find_last_dir_sep(resolved);
	if (slash)
		resolved[slash - resolved] = '\0';

	executable_dirname = resolved;
	trace_printf("trace: resolved executable dir: %s\n",
		     executable_dirname);
}

#else

/**
 * When not using a runtime prefix, Git uses a hard-coded path, and there is
 * nothing to resolve.
 */

static const char *system_prefix(void)
{
	return PREFIX;
}

void git_resolve_executable_dir(const char *argv0)
{
}

#endif /* RUNTIME_PREFIX */

char *system_path(const char *path)
{
	struct strbuf d = STRBUF_INIT;

	if (is_absolute_path(path))
		return xstrdup(path);

	strbuf_addf(&d, "%s/%s", system_prefix(), path);
	return strbuf_detach(&d, NULL);
}

static const char *exec_path_value;

void git_set_exec_path(const char *exec_path)
{
	exec_path_value = exec_path;
	/*
	 * Propagate this setting to external programs.
	 */
	setenv(EXEC_PATH_ENVIRONMENT, exec_path, 1);
}

/* Returns the highest-priority location to look for git programs. */
const char *git_exec_path(void)
{
	if (!exec_path_value) {
		const char *env = getenv(EXEC_PATH_ENVIRONMENT);
		if (env && *env)
			exec_path_value = xstrdup(env);
		else
			exec_path_value = system_path(GIT_EXEC_PATH);
	}
	return exec_path_value;
}

static void add_path(struct strbuf *out, const char *path)
{
	if (path && *path) {
		strbuf_add_absolute_path(out, path);
		strbuf_addch(out, PATH_SEP);
	}
}

void setup_path(void)
{
	const char *exec_path = git_exec_path();
	const char *old_path = getenv("PATH");
	struct strbuf new_path = STRBUF_INIT;

	git_set_exec_path(exec_path);
	add_path(&new_path, exec_path);

	if (old_path)
		strbuf_addstr(&new_path, old_path);
	else
		strbuf_addstr(&new_path, _PATH_DEFPATH);

	setenv("PATH", new_path.buf, 1);

	strbuf_release(&new_path);
}

const char **prepare_git_cmd(struct argv_array *out, const char **argv)
{
	argv_array_push(out, "git");
	argv_array_pushv(out, argv);
	return out->argv;
}

int execv_git_cmd(const char **argv)
{
	struct argv_array nargv = ARGV_ARRAY_INIT;

	prepare_git_cmd(&nargv, argv);
	trace_argv_printf(nargv.argv, "trace: exec:");

	/* execvp() can only ever return if it fails */
	sane_execvp("git", (char **)nargv.argv);

	trace_printf("trace: exec failed: %s\n", strerror(errno));

	argv_array_clear(&nargv);
	return -1;
}

int execl_git_cmd(const char *cmd, ...)
{
	int argc;
	const char *argv[MAX_ARGS + 1];
	const char *arg;
	va_list param;

	va_start(param, cmd);
	argv[0] = cmd;
	argc = 1;
	while (argc < MAX_ARGS) {
		arg = argv[argc++] = va_arg(param, char *);
		if (!arg)
			break;
	}
	va_end(param);
	if (MAX_ARGS <= argc)
		return error("too many args to run %s", cmd);

	argv[argc] = NULL;
	return execv_git_cmd(argv);
}