using Astralis;
using Invercargill;
using Invercargill.DataStructures;

namespace Statum.Tools {

    /**
     * `statum-mkres` — generates a {@link Statum.ConstantStatumResource} Vala
     * subclass from an input file, precompressing it with identity/gzip/zstd/br.
     *
     * Mirrors `spry-mkssr --vala`. Intended to be wired as a meson
     * `custom_target` (see `tools/meson.build`).
     *
     *     statum-mkres -o LogoResource.vala -n logo.png logo.png
     *     statum-mkres --ns MyApp.Static -c text/css -o Styles.vala styles.css
     */
    public class Mkres : Object {

        private static string? output_file = null;
        private static string? content_type_override = null;
        private static string? resource_name_override = null;
        private static string? class_name_override = null;
        private static string? namespace_name = null;

        private const OptionEntry[] options = {
            { "output", 'o', 0, OptionArg.FILENAME, ref output_file, "Output Vala file name (default: <InputName>Resource.vala)", "FILE" },
            { "content-type", 'c', 0, OptionArg.STRING, ref content_type_override, "Override content type (e.g. text/html)", "TYPE" },
            { "name", 'n', 0, OptionArg.STRING, ref resource_name_override, "Resource name (default: input filename)", "NAME" },
            { "class-name", '\0', 0, OptionArg.STRING, ref class_name_override, "Generated Vala class name (default: <Name>Resource)", "CLASS" },
            { "ns", '\0', 0, OptionArg.STRING, ref namespace_name, "Namespace for the generated class", "NAMESPACE" },
            { null }
        };

        public static int main(string[] args) {
            try {
                var opt_context = new OptionContext("INPUT_FILE - Generate a Statum ConstantStatumResource");
                opt_context.add_main_entries(options, null);
                opt_context.parse(ref args);
            } catch (OptionError e) {
                stderr.printf("Error: %s\n", e.message);
                return 1;
            }

            string? input_file = null;
            if (args.length > 1) {
                input_file = args[1];
            }
            if (input_file == null) {
                stderr.printf("Error: No input file specified.\n");
                return 1;
            }

            var name = resource_name_override ?? Path.get_basename((!)input_file);
            var class_name_base = resource_name_override ?? Path.get_basename((!)input_file);
            var output_path = output_file ?? (make_pascal_case(class_name_base) + "Resource.vala");
            var class_name = class_name_override ?? (make_pascal_case(class_name_base) + "Resource");

            try {
                var tool = new Mkres();
                var generated = tool.process((!)input_file, name, class_name, content_type_override, namespace_name);
                write_file(output_path, generated);
                stdout.printf("Generated: %s\n", output_path);
                return 0;
            } catch (Error e) {
                stderr.printf("Error: %s\n", e.message);
                return 1;
            }
        }

        public string process(string input_path, string name, string class_name, string? content_type_override, string? namespace_name) throws Error {
            var input_data = read_all(input_path);

            string content_type;
            if (content_type_override != null) {
                content_type = (!)content_type_override;
            } else {
                content_type = guess_content_type(name, input_data);
            }

            var hash_hex = compute_hash_hex(input_data);
            var encodings = compress_all(input_data);

            return emit_vala(class_name, name, content_type, hash_hex, encodings, namespace_name);
        }

        private EncodedData[] compress_all(uint8[] input_data) {
            var encodings = new EncodedData[0];

            var identity_data = new uint8[input_data.length];
            Memory.copy(identity_data, input_data, input_data.length);
            encodings += new EncodedData("identity", (owned)identity_data);

            var input_buffer = new ByteBuffer.from_byte_array(input_data);

            // GZip
            var gzip = new GzipCompressor(9).compress_buffer(input_buffer, null).to_array();
            if (gzip.length < input_data.length) {
                encodings += new EncodedData("gzip", (owned)gzip);
            }
            // Zstandard
            var zstd = new ZstdCompressor(19).compress_buffer(input_buffer, null).to_array();
            if (zstd.length < input_data.length) {
                encodings += new EncodedData("zstd", (owned)zstd);
            }
            // Brotli
            var br = new BrotliCompressor(11).compress_buffer(input_buffer, null).to_array();
            if (br.length < input_data.length) {
                encodings += new EncodedData("br", (owned)br);
            }

            return encodings;
        }

        private string emit_vala(string class_name, string name, string content_type, string hash_hex, EncodedData[] encodings, string? namespace_name) {
            var b = new StringBuilder();

            string i1 = namespace_name != null ? "    " : "";
            string i2 = namespace_name != null ? "        " : "    ";
            string i3 = namespace_name != null ? "            " : "        ";
            string i4 = namespace_name != null ? "                " : "            ";

            b.append("using Statum;\n");
            b.append("using Invercargill;\n");
            b.append("using Invercargill.DataStructures;\n\n");

            if (namespace_name != null) {
                b.append_printf("namespace %s {\n\n", namespace_name);
            }

            b.append_printf("%s// Generated by statum-mkres\n", i1);
            b.append_printf("%spublic class %s : ConstantStatumResource {\n\n", i1, class_name);

            b.append_printf("%spublic override string name { get { return \"%s\"; } }\n", i2, escape(name));
            b.append_printf("%spublic override string file_hash { get { return \"%s\"; } }\n", i2, hash_hex);
            b.append_printf("%spublic override string content_type { get { return \"%s\"; } }\n\n", i2, escape(content_type));

            // Order by size so the client gets the smallest supported encoding.
            var ordered = sort_by_size(encodings);

            b.append_printf("%spublic override string get_best_encoding(Set<string> supported) {\n", i2);
            foreach (var encoding in ordered) {
                if (encoding.type == "identity") {
                    continue;
                }
                b.append_printf("%sif (supported.has(\"%s\")) return \"%s\";\n", i3, encoding.type, encoding.type);
            }
            b.append_printf("%sreturn \"identity\";\n", i3);
            b.append_printf("%s}\n\n", i2);

            b.append_printf("%spublic override unowned uint8[] get_encoding(string encoding) {\n", i2);
            b.append_printf("%sswitch (encoding) {\n", i3);
            foreach (var encoding in encodings) {
                var var_name = encoding_const(encoding.type);
                b.append_printf("%scase \"%s\": return %s;\n", i4, encoding.type, var_name);
            }
            b.append_printf("%sdefault: return IDENTITY_DATA;\n", i4);
            b.append_printf("%s}\n", i3);
            b.append_printf("%s}\n\n", i2);

            foreach (var encoding in encodings) {
                var var_name = encoding_const(encoding.type);
                b.append_printf("%sprivate const uint8[] %s = {\n", i2, var_name);
                append_byte_array(b, encoding.data, i3);
                b.append_printf("\n%s};\n\n", i2);
            }

            b.append_printf("%s}\n", i1);
            if (namespace_name != null) {
                b.append("}\n");
            }

            return b.str;
        }

        private static EncodedData[] sort_by_size(EncodedData[] encodings) {
            var copy = new EncodedData[encodings.length];
            for (var i = 0; i < encodings.length; i++) {
                copy[i] = encodings[i];
            }
            for (var i = 0; i < copy.length - 1; i++) {
                for (var j = i + 1; j < copy.length; j++) {
                    if (copy[i].data.length > copy[j].data.length) {
                        var tmp = copy[i];
                        copy[i] = copy[j];
                        copy[j] = tmp;
                    }
                }
            }
            return copy;
        }

        private static string encoding_const(string encoding_type) {
            return encoding_type.replace("-", "_").up() + "_DATA";
        }

        private static void append_byte_array(StringBuilder b, uint8[] data, string indent) {
            for (var i = 0; i < data.length; i++) {
                if (i == 0) {
                    b.append(indent);
                } else if (i % 16 == 0) {
                    b.append(",\n").append(indent);
                } else {
                    b.append(", ");
                }
                b.append_printf("0x%02x", data[i]);
            }
        }

        private static string escape(string s) {
            return s.replace("\\", "\\\\").replace("\"", "\\\"");
        }

        private static string guess_content_type(string filename, uint8[] sample_data) {
            bool uncertain;
            var content_type = ContentType.guess(filename, sample_data, out uncertain);
            var mime = ContentType.get_mime_type(content_type);
            return mime ?? "application/octet-stream";
        }

        private static string compute_hash_hex(uint8[] data) {
            var checksum = new Checksum(ChecksumType.SHA512);
            checksum.update(data, data.length);
            return checksum.get_string();
        }

        private static uint8[] read_all(string path) throws Error {
            var file = File.new_for_path(path);
            if (!file.query_exists()) {
                throw new IOError.NOT_FOUND(@"Input file '$path' does not exist");
            }
            var size = (size_t) file.query_info("standard::size", 0).get_size();
            var stream = new DataInputStream(file.read());
            var bytes = stream.read_bytes(size);
            stream.close();
            var data = new uint8[bytes.get_size()];
            Memory.copy(data, bytes.get_data(), bytes.get_size());
            return data;
        }

        private static void write_file(string path, string contents) throws Error {
            var file = File.new_for_path(path);
            var stream = new DataOutputStream(file.replace(null, false, FileCreateFlags.NONE));
            stream.put_string(contents);
            stream.close();
        }

        private static string make_pascal_case(string input) {
            var name = input;
            var dot = name.last_index_of(".");
            if (dot > 0) {
                name = name.substring(0, dot);
            }
            var result = new StringBuilder();
            var capitalize_next = true;
            foreach (var c in name.data) {
                if (c == '-' || c == '_' || c == ' ' || c == '.') {
                    capitalize_next = true;
                } else {
                    if (capitalize_next) {
                        result.append_printf("%c", c >= 'a' && c <= 'z' ? c - 32 : c);
                        capitalize_next = false;
                    } else {
                        result.append_printf("%c", c);
                    }
                }
            }
            return result.str;
        }

        private class EncodedData {
            public string type;
            public uint8[] data;

            public EncodedData(string type, owned uint8[] data) {
                this.type = type;
                this.data = (owned)data;
            }
        }
    }
}