fetch: Add new executable

1 files changed, 159 insertions, 0 deletions

diff --git a/fetch/fetch.cc b/fetch/fetch.cc
new file mode 100644
index 0000000..941051f
--- /dev/null
+++ b/fetch/fetch.cc
@@ -0,0 +1,159 @@
+/*
+ * fetch.cc - Implementation of the HorizonScript Locator
+ * Project Horizon
+ *
+ * Copyright (c) 2019 Adélie Linux and contributors.  All rights reserved.
+ * This code is licensed under the AGPL 3.0 license, as noted in the
+ * LICENSE-code file in the root directory of this repository.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#include <algorithm>        /* transform */
+#include <cstdlib>          /* EXIT_* */
+#include <fstream>
+#include <map>
+#include <string>
+#include <unistd.h>         /* access */
+#include "util/output.hh"
+
+static const char *IFILE_PATH = "/etc/horizon/installfile";
+static const int SCRIPT_LINE_MAX = 512;
+
+bool pretty = true;
+
+/*! Process a local path and copy it to the proper location.
+ * @param path      The local path.
+ * @returns An exit code.
+ */
+int process_local(const std::string &path) {
+    /* if we can't read it, don't even bother */
+    if(access(path.c_str(), R_OK) != 0) {
+        output_error("process_local",
+                     std::string(path) + " does not exist or is not readable");
+        return EXIT_FAILURE;
+    }
+
+    std::ofstream output(IFILE_PATH, std::ios_base::trunc);
+    if(!output) {
+        output_error("process_local",
+                     std::string(IFILE_PATH) +
+                     " could not be opened for writing");
+        return EXIT_FAILURE;
+    }
+    std::ifstream input(path, std::ios_base::in);
+    if(!input) {
+        output_error("process_local",
+                     path + " could not be opened for reading");
+        return EXIT_FAILURE;
+    }
+    char buffer[SCRIPT_LINE_MAX];
+
+    while(input.getline(buffer, SCRIPT_LINE_MAX)) {
+        output << buffer << std::endl;
+    }
+
+    if(input.fail() && !input.eof()) {
+        output_error("process_local", "line length error reading " + path);
+        return EXIT_FAILURE;
+    }
+    if(input.bad() && !input.eof()) {
+        output_error("process_local", "I/O error reading " + path);
+        return EXIT_FAILURE;
+    }
+
+    return EXIT_SUCCESS;
+}
+
+
+/*! Download an installfile using cURL.
+ * @param path      The remote path to download.
+ */
+int process_curl(const std::string &path) {
+    return EXIT_FAILURE;
+}
+
+
+/*! The signature of a protocol dispatch function */
+typedef int (*proto_dispatch_fn)(const std::string &);
+
+
+/*! Protocol handlers */
+static const std::map<std::string, proto_dispatch_fn> protos = {
+    {"http", process_curl},
+    {"https", process_curl},
+    {"tftp", process_curl}
+};
+
+
+/*! Dispatch handling of +path+ to a protocol handler, or return failure.
+ * @param path      The remote path to download to IFILE_PATH.
+ * @returns EXIT_SUCCESS if the file was downloaded; EXIT_FAILURE otherwise.
+ * @note Currently, it is ambiguous whether EXIT_FAILURE means invalid proto
+ * or error downloading from the URL.
+ */
+int process_maybe_remote(const std::string &path) {
+    std::string proto = path.substr(0, path.find_first_of(":"));
+    std::transform(proto.begin(), proto.end(), proto.begin(), ::tolower);
+
+    if(protos.find(proto) != protos.end()) {
+        return (*protos.at(proto))(path);
+    }
+
+    std::string support = "This build of Horizon supports: ";
+    for(auto &proto_pair : protos) {
+        support += proto_pair.first + " ";
+    }
+
+    output_error("argv", proto + " is not a valid protocol", support);
+    return EXIT_FAILURE;
+}
+
+
+/*
+ * The goal of the Locator is to find the HorizonScript for this computer,
+ * which is the target, and copy it to the well-known path /etc/horizon
+ * as 'installfile'.
+ */
+int main(int argc, char *argv[]) {
+    std::string installfile;
+
+    if(argc < 1 || argc > 2) {
+        std::cerr << "usage: " << std::endl;
+        std::cerr << "\thscript-fetch [path|url]" << std::endl;
+        return EXIT_FAILURE;
+    }
+
+    bold_if_pretty(std::cout);
+    std::cout << "HorizonScript Locator version " << VERSTR;
+    reset_if_pretty(std::cout);
+    std::cout << std::endl;
+    std::cout << "Copyright (c) 2019 Adélie Linux and contributors.  AGPL-3.0 license." << std::endl;
+    std::cout << std::endl;
+
+    if(argc == 1) {
+        if(access(IFILE_PATH, F_OK) == 0) {
+            /* That was easy™ */
+            std::cout << "HorizonScript already present at " << IFILE_PATH
+                      << ".  Quitting." << std::endl;
+            return EXIT_SUCCESS;
+        }
+
+        output_error("internal", "Fully Remote HorizonScript downloading "
+                     "is not yet implemented");
+        return EXIT_FAILURE;
+    }
+
+    std::string path(argv[1]);
+
+    if(path[0] == '/') {
+        return process_local(path);
+    }
+    if(path.find("://") != std::string::npos) {
+        return process_maybe_remote(path);
+    }
+
+    output_error("argv", "Unrecognised protocol or invalid URL",
+                 "An absolute path or URL is required");
+    return EXIT_FAILURE;
+}