using GLib;
using Json;

namespace Spry.Cli {

    /**
     * `spry keys` — runs `statum-genkeys` and merges its key material into
     * the "statum" section of the application's `web-config.json`.
     *
     * Key material is maintained as PAIRS (a secret and its public half):
     * when either half of a pair is missing the whole pair is regenerated,
     * so a half-deleted file is repaired with a matching pair rather than a
     * mismatched one. Any run that (re)writes key material prints a
     * prominent warning: regenerating a pair invalidates existing sessions
     * and sealed blobs. Complete pairs and every other configuration
     * section are left untouched.
     */
    public class Keys : GLib.Object {

        /**
         * The static key fields Statum reads from the "statum" section,
         * ordered secret/public pair-wise so missing halves can be repaired
         * by regenerating the whole pair.
         */
        public const string[] STATUM_KEYS = {
            "signing_secret_key",
            "signing_public_key",
            "encryption_signing_secret_key",
            "encryption_signing_public_key",
            "encryption_sealing_secret_key",
            "encryption_sealing_public_key"
        };

        /**
         * Fills any missing "statum" key pairs in `config_path`, creating
         * the file (and the section) when absent, and repairs half-present
         * pairs by regenerating them whole. Does nothing when every key is
         * already configured.
         */
        public static void run(string config_path, string? tools_dir, string? libdir) throws Error {
            if (has_all_keys(config_path)) {
                stdout.printf("All static keys are already configured in %s — nothing to do.\n", config_path);
                return;
            }

            var generated = spawn_genkeys(tools_dir, libdir);
            string[] repaired;
            var added = merge(config_path, generated, out repaired);
            foreach (var key in added) {
                stdout.printf("Added %s to the statum section of %s\n", key, config_path);
            }
            foreach (var pair in repaired) {
                stdout.printf("Repaired an incomplete pair in %s — %s were regenerated\n", config_path, pair);
            }
            stderr.printf("*** WARNING: new static key material was generated in %s.\n", config_path);
            stderr.printf("*** Existing sessions and sealed blobs are invalidated by this change.\n");
        }

        private static bool has_all_keys(string config_path) {
            if (!FileUtils.test(config_path, FileTest.EXISTS)) {
                return false;
            }
            try {
                var parser = new Parser();
                parser.load_from_file(config_path);
                var root = parser.get_root();
                if (root == null || root.get_object() == null || !((!)root).get_object().has_member("statum")) {
                    return false;
                }
                var statum = ((!)root).get_object().get_object_member("statum");
                foreach (var key in STATUM_KEYS) {
                    if (!statum.has_member(key) || statum.get_string_member(key) == null
                        || ((!)statum.get_string_member(key)).length == 0) {
                        return false;
                }
                }
                return true;
            } catch (Error e) {
                return false;
            }
        }

        private static Json.Object spawn_genkeys(string? tools_dir, string? libdir) throws Error {
            var tool = Tools.resolve("statum-genkeys", tools_dir);
            var launcher = new SubprocessLauncher(SubprocessFlags.STDOUT_PIPE | SubprocessFlags.STDERR_PIPE);
            Tools.apply_env(launcher, libdir);
            var process = launcher.spawnv({ tool });

            string stdout_buf;
            string stderr_buf;
            process.communicate_utf8(null, null, out stdout_buf, out stderr_buf);
            if (!process.get_successful()) {
                throw Generator.cli_error("statum-genkeys failed: %s", (stderr_buf ?? "").strip());
            }

            var parser = new Parser();
            parser.load_from_data(stdout_buf ?? "");
            var root = parser.get_root();
            if (root == null || root.get_object() == null || !((!)root).get_object().has_member("statum")) {
                throw Generator.cli_error("unexpected statum-genkeys output");
            }
            return ((!)root).get_object().get_object_member("statum");
        }

        /**
         * Merges the generated material pair-wise: complete pairs are kept,
         * pairs with a missing half are regenerated whole (`repaired` lists
         * them as `"secret + public"` labels), entirely absent pairs are
         * added (`added` lists their keys). The file is rewritten with mode
         * 0600 because it carries key material.
         */
        private static string[] merge(string config_path, Json.Object generated, out string[] repaired) throws Error {
            repaired = new string[0];
            var root = new Json.Object();
            if (FileUtils.test(config_path, FileTest.EXISTS)) {
                var parser = new Parser();
                try {
                    parser.load_from_file(config_path);
                } catch (Error e) {
                    throw Generator.cli_error("%s is not valid JSON: %s", config_path, e.message);
                }
                var existing = parser.get_root();
                if (existing == null || existing.get_object() == null) {
                    throw Generator.cli_error("%s has no JSON object at the top level", config_path);
                }
                root = ((!)existing).get_object();
            }

            if (!root.has_member("statum")) {
                root.set_object_member("statum", new Json.Object());
            }
            var statum = root.get_object_member("statum");

            var added = new string[0];
            var repaired_pairs = new string[0];
            for (int i = 0; i + 1 < STATUM_KEYS.length; i += 2) {
                var secret_key = STATUM_KEYS[i];
                var public_key = STATUM_KEYS[i + 1];
                var secret = member_value(statum, secret_key);
                var public_value = member_value(statum, public_key);
                if (secret.length > 0 && public_value.length > 0) {
                    continue;
                }
                if (secret.length > 0 || public_value.length > 0) {
                    repaired_pairs += secret_key + " + " + public_key;
                } else {
                    added += secret_key;
                    added += public_key;
                }
                statum.set_string_member(secret_key, generated_value(generated, secret_key));
                statum.set_string_member(public_key, generated_value(generated, public_key));
            }
            repaired = repaired_pairs;

            var node = new Json.Node(Json.NodeType.OBJECT);
            node.set_object(root);
            Generator.write_file(config_path, Json.to_string(node, true) + "\n", 0600);
            return added;
        }

        private static string member_value(Json.Object obj, string key) {
            if (!obj.has_member(key) || obj.get_string_member(key) == null) {
                return "";
            }
            return ((!)obj.get_string_member(key)) ?? "";
        }

        private static string generated_value(Json.Object generated, string key) throws Error {
            if (!generated.has_member(key) || generated.get_string_member(key) == null) {
                throw Generator.cli_error("statum-genkeys output lacks %s", key);
            }
            return (!)generated.get_string_member(key);
        }
    }
}