battle_ui.ts

function highlight_outline(cell_index_to_highlight: boolean[], color: XYZ) {
    const cell_index_to_edges: Array<{ edge: Edge, from: XY, to: XY, deleted: boolean }[]> = [];
    const unique_edges: { edge: Edge, from: XY, to: XY, deleted: boolean }[] = [];

    function merge_edges(at: XY, going_towards: Edge, right_relative: number | undefined, left_relative: number | undefined, index: number) {
        const right_neighbor = right_relative && cell_index_to_edges[right_relative];
        const right_edge = right_neighbor && right_neighbor.find(old => old.edge == going_towards);
        const left_neighbor = left_relative && cell_index_to_edges[left_relative];
        const left_edge = left_neighbor && left_neighbor.find(old => old.edge == going_towards);

        if (right_edge && left_edge) {
            right_edge.to = left_edge.to;
            left_edge.deleted = true;
            cell_index_to_edges[index].push(right_edge);
        } else {
            if (right_edge) {
                right_edge.to = at;
                cell_index_to_edges[index].push(right_edge);
            }

            if (left_edge) {
                left_edge.from = at;
                cell_index_to_edges[index].push(left_edge);
            }
        }

        if (!right_edge && !left_edge) {
            const new_edge = { edge: going_towards, from: at, to: at, deleted: false };
            cell_index_to_edges[index].push(new_edge);
            unique_edges.push(new_edge);
        }
    }

    for (let index = 0; index < cell_index_to_highlight.length; index++) {
        const is_highlighted = cell_index_to_highlight[index];

        if (!is_highlighted) continue;

        const cell = battle.cells[index];
        const at = cell.position;

        const right = grid_cell_index_raw(battle, at.x + 1, at.y);
        const left = grid_cell_index_raw(battle, at.x - 1, at.y);
        const top = grid_cell_index_raw(battle, at.x, at.y + 1);
        const bottom = grid_cell_index_raw(battle, at.x, at.y - 1);

        const edge_side_right_left: [Edge, number | undefined, number | undefined, number | undefined][] = [
            [ Edge.top, top, right, left ],
            [ Edge.bottom, bottom, left, right ],
            [ Edge.right, right, bottom, top ],
            [ Edge.left, left, top, bottom ]
        ];

        for (const [ edge, side, right, left ] of edge_side_right_left) {
            if (side == undefined || !cell_index_to_highlight[side]) {
                if (!cell_index_to_edges[index]) {
                    cell_index_to_edges[index] = [];
                }

                merge_edges(cell.position, edge, right, left, index);
            }
        }
    }

    const half = battle_cell_size / 2;
    const height = 160;

    for (const { edge, from, to, deleted } of unique_edges) {
        if (deleted) continue;

        const fx = Particles.CreateParticle("particles/ui/highlight_rope.vpcf", ParticleAttachment_t.PATTACH_CUSTOMORIGIN, 0);

        const [fr_x, fr_y, fr_z] = battle_position_to_world_position_center(from);
        const [to_x, to_y, to_z] = battle_position_to_world_position_center(to);

        switch (edge) {
            case Edge.bottom: {
                Particles.SetParticleControl(fx, 0, [fr_x - half, fr_y - half, fr_z + height]);
                Particles.SetParticleControl(fx, 1, [to_x + half, to_y - half, to_z + height]);

                break;
            }

            case Edge.top: {
                Particles.SetParticleControl(fx, 0, [fr_x + half, fr_y + half, fr_z + height]);
                Particles.SetParticleControl(fx, 1, [to_x - half, to_y + half, to_z + height]);

                break;
            }

            case Edge.left: {
                Particles.SetParticleControl(fx, 0, [fr_x - half, fr_y + half, fr_z + height]);
                Particles.SetParticleControl(fx, 1, [to_x - half, to_y - half, to_z + height]);

                break;
            }

            case Edge.right: {
                Particles.SetParticleControl(fx, 0, [fr_x + half, fr_y - half, fr_z + height]);
                Particles.SetParticleControl(fx, 1, [to_x + half, to_y + half, to_z + height]);

                break;
            }
        }

        Particles.SetParticleControl(fx, 2, color);

        register_particle_for_reload(fx);
    }
}