layout(location = 0) in vec4 a_pos_offset;
layout(location = 1) in uvec4 a_data;
layout(location = 2) in vec3 a_projected_pos;
layout(location = 3) in uint a_fade_opacity;

// contents of a_size vary based on the type of property value
// used for {text,icon}-size.
// For constants, a_size is disabled.
// For source functions, we bind only one value per vertex: the value of {text,icon}-size evaluated for the current feature.
// For composite functions:
// [ text-size(lowerZoomStop, feature),
//   text-size(upperZoomStop, feature) ]
uniform bool u_is_size_zoom_constant;
uniform bool u_is_size_feature_constant;
uniform highp float u_size_t; // used to interpolate between zoom stops when size is a composite function
uniform highp float u_size; // used when size is both zoom and feature constant
uniform mat4 u_label_plane_matrix;
uniform mat4 u_coord_matrix;
uniform bool u_is_text;
uniform bool u_pitch_with_map;
uniform highp float u_pitch;
uniform bool u_rotate_symbol;
uniform highp float u_aspect_ratio;
uniform highp float u_camera_to_center_distance;
uniform float u_fade_change;
uniform vec2 u_texsize;
uniform vec2 u_texsize_icon;
uniform bool u_is_along_line;
uniform bool u_is_variable_anchor;
uniform vec2 u_translation;
uniform float u_pitched_scale;
uniform bool u_is_offset;

out vec4 v_data0;
out vec3 v_data1;
flat out float v_is_sdf;

#pragma maplibre: define highp vec4 fill_color
#pragma maplibre: define highp vec4 halo_color
#pragma maplibre: define lowp float opacity
#pragma maplibre: define lowp float halo_width
#pragma maplibre: define lowp float halo_blur

void main() {
    #pragma maplibre: initialize highp vec4 fill_color
    #pragma maplibre: initialize highp vec4 halo_color
    #pragma maplibre: initialize lowp float opacity
    #pragma maplibre: initialize lowp float halo_width
    #pragma maplibre: initialize lowp float halo_blur

    vec2 a_pos = a_pos_offset.xy;
    vec2 a_offset = a_pos_offset.zw;

    vec2 a_tex = vec2(a_data.xy);
    vec2 a_size = vec2(a_data.zw);

    float a_size_min = float(a_data.z >> 1u);
    float is_sdf = float(a_data.z & 1u);

    float ele = get_elevation(a_pos);
    highp float segment_angle = -a_projected_pos[2];
    float size;

    if (!u_is_size_zoom_constant && !u_is_size_feature_constant) {
        size = mix(a_size_min, a_size[1], u_size_t) / 128.0;
    } else if (u_is_size_zoom_constant && !u_is_size_feature_constant) {
        size = a_size_min / 128.0;
    } else {
        size = u_size;
    }

    vec2 translated_a_pos = a_pos + u_translation;
    vec4 projectedPoint = projectTileWithElevation(translated_a_pos, ele);

    // compute total opacity and early exit if too transparent:
    vec2 fade_opacity = unpack_opacity(a_fade_opacity);
    float visibility = calculate_visibility(projectedPoint);
    float fade_change = fade_opacity[1] > 0.5 ? u_fade_change : -u_fade_change;
    float interpolated_fade_opacity = max(0.0, min(visibility, fade_opacity[0] + fade_change));
    float total_opacity = opacity * interpolated_fade_opacity;
    if (total_opacity < 0.1){
        gl_Position = vec4(-2., -2., -2., 1.);
        return;
    }

    highp float camera_to_anchor_distance = projectedPoint.w;
    // If the label is pitched with the map, layout is done in pitched space,
    // which makes labels in the distance smaller relative to viewport space.
    // We counteract part of that effect by multiplying by the perspective ratio.
    // If the label isn't pitched with the map, we do layout in viewport space,
    // which makes labels in the distance larger relative to the features around
    // them. We counteract part of that effect by dividing by the perspective ratio.
    highp float distance_ratio = u_pitch_with_map ?
        camera_to_anchor_distance / u_camera_to_center_distance :
        u_camera_to_center_distance / camera_to_anchor_distance;
    highp float perspective_ratio = clamp(
        0.5 + 0.5 * distance_ratio,
        0.0, // Prevents oversized near-field symbols in pitched/overzoomed tiles
        4.0);

    if (!u_is_offset) {
        size *= perspective_ratio;
    }

    float fontScale = size / 24.0;

    highp float symbol_rotation = 0.0;
    if (u_rotate_symbol) {
        // See comments in symbol_sdf.vertex
        vec4 offsetProjectedPoint = projectTileWithElevation(translated_a_pos + vec2(1, 0), ele);

        vec2 a = projectedPoint.xy / projectedPoint.w;
        vec2 b = offsetProjectedPoint.xy / offsetProjectedPoint.w;

        symbol_rotation = atan((b.y - a.y) / u_aspect_ratio, b.x - a.x);
    }

    highp float angle_sin = sin(segment_angle + symbol_rotation);
    highp float angle_cos = cos(segment_angle + symbol_rotation);
    mat2 rotation_matrix = mat2(angle_cos, -1.0 * angle_sin, angle_sin, angle_cos);

    vec4 projected_pos;
    if (u_is_along_line || u_is_variable_anchor) {
        projected_pos = vec4(a_projected_pos.xy, ele, 1.0);
    } else if (u_pitch_with_map) {
        projected_pos = u_label_plane_matrix * vec4(a_projected_pos.xy + u_translation, ele, 1.0);
    } else {
        projected_pos = u_label_plane_matrix * projectTileWithElevation(a_projected_pos.xy + u_translation, ele);
    }

    float z = float(u_pitch_with_map) * projected_pos.z / projected_pos.w;

    float projectionScaling = 1.0;
#ifdef GLOBE
    if(u_pitch_with_map && !u_is_along_line) {
        float anchor_pos_tile_y = (u_coord_matrix * vec4(projected_pos.xy / projected_pos.w, z, 1.0)).y;
        projectionScaling = mix(projectionScaling, 1.0 / circumferenceRatioAtTileY(anchor_pos_tile_y) * u_pitched_scale, u_projection_transition);
    }
#endif

    vec4 finalPos = u_coord_matrix * vec4(projected_pos.xy / projected_pos.w + rotation_matrix * (a_offset / 32.0 * fontScale) * projectionScaling, z, 1.0);
    if(u_pitch_with_map) {
        finalPos = projectTileWithElevation(finalPos.xy, finalPos.z);
    }
    float gamma_scale = finalPos.w;
    gl_Position = finalPos;

    v_data0.xy = a_tex / u_texsize;
    v_data0.zw = a_tex / u_texsize_icon;
    v_data1 = vec3(gamma_scale, size, total_opacity);
    v_is_sdf = is_sdf;
}