// Protocol Version 1

package mapnik.vector;

option optimize_for = LITE_RUNTIME;

message tile {
        enum GeomType {
             Unknown = 0;
             Point = 1;
             LineString = 2;
             Polygon = 3;
        }

        // Variant type encoding
        message value {
                // Exactly one of these values may be present in a valid message
                optional string string_value = 1;
                optional float float_value = 2;
                optional double double_value = 3;
                optional int64 int_value = 4;
                optional uint64 uint_value = 5;
                optional sint64 sint_value = 6;
                optional bool bool_value = 7;

                extensions 8 to max;
        }

        message feature {
                optional uint64 id = 1;

                // Tags of this feature. Even numbered values refer to the nth
                // value in the keys list on the tile message, odd numbered
                // values refer to the nth value in the values list on the tile
                // message.
                repeated uint32 tags = 2 [ packed = true ];

                // The type of geometry stored in this feature.
                optional GeomType type = 3 [ default = Unknown ];

                // Contains a stream of commands and parameters (vertices). The
                // repeat count is shifted to the left by 3 bits. This means
                // that the command has 3 bits (0-7). The repeat count
                // indicates how often this command is to be repeated. Defined
                // commands are:
                // - MoveTo:    1   (2 parameters follow)
                // - LineTo:    2   (2 parameters follow)
                // - ClosePath: 7   (no parameters follow)
                //
                // Commands are encoded as uint32 varints. Vertex parameters
                // are encoded as deltas to the previous position and, as they
                // may be negative, are further "zigzag" encoded as unsigned
                // 32-bit ints:
                //
                //   n = (n << 1) ^ (n >> 31)
                //
                // Ex.: MoveTo(3, 6), LineTo(8, 12), LineTo(20, 34), ClosePath
                // Encoded as: [ 9 6 12 18 10 12 24 44 15 ]
                //               |       |              `> [00001 111] command type 7 (ClosePath), length 1
                //               |       |       ===== relative LineTo(+12, +22) == LineTo(20, 34)
                //               |       | ===== relative LineTo(+5, +6) == LineTo(8, 12)
                //               |       `> [00010 010] = command type 2 (LineTo), length 2
                //               | ==== relative MoveTo(+3, +6)
                //               `> [00001 001] = command type 1 (MoveTo), length 1
                //
                // The original position is (0,0).
                repeated uint32 geometry = 4 [ packed = true ];
        }

        message layer {
                // Any compliant implementation must first read the version
                // number encoded in this message and choose the correct
                // implementation for this version number before proceeding to
                // decode other parts of this message.
                required uint32 version = 15 [ default = 1 ];

                required string name = 1;

                // The actual features in this tile.
                repeated feature features = 2;

                // Dictionary encoding for keys
                repeated string keys = 3;

                // Dictionary encoding for values
                repeated value values = 4;

                // The bounding box in this tile spans from 0..4095 units
                optional uint32 extent = 5 [ default = 4096 ];

                extensions 16 to max;
        }

        repeated layer layers = 3;

        extensions 16 to 8191;
}
