slippy.hpp

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// Andrew Naplavkov
 
#ifndef BOAT_SLIPPY_HPP
#define BOAT_SLIPPY_HPP
 
#include <boat/db/catalog.hpp>
#include <boat/detail/curl.hpp>
#include <boat/detail/numbers.hpp>
 
namespace boat::slippy {
 
class catalog : public db::catalog {
    inline static auto err = std::logic_error{"slippy"};
 
public:
    std::string url;    
    std::string agent;  
    int epsg = 3857;    
    int ssl = 1;        
    int zmax = 19;      
 
    std::vector<db::source> sources() override { return {}; }
 
    std::vector<db::layer> layers() override
    {
        return {{"", "_layer", "raster", true}};
    }
 
    db::table get_table(std::string_view, std::string_view) override
    {
        throw err;
    }
 
    db::rowset select(db::table const&, db::page const&) override { throw err; }
 
    db::rowset select(db::table const&, db::bbox const&) override { throw err; }
 
    void insert(  //
        db::table const&,
        db::rowset const&,
        std::stop_token = {}) override
    {
        throw err;
    }
 
    db::table create(db::table const&) override { throw err; }
 
    void drop(std::string_view, std::string_view) override {}
 
    db::raster get_raster(db::layer const&) override
    {
        auto lim =
            std::nexttoward(numbers::pi * numbers::earth::equatorial_radius, 0);
        auto sz = tile::size * pow2(zmax);
        return {
            .table_name{"_layer"},
            .column_name{"raster"},
            .bands{{"red", "byte"},
                   {"green", "byte"},
                   {"blue", "byte"},
                   {"alpha", "byte"}},
            .width = sz,
            .height = sz,
            .xorig = -lim,
            .yorig = lim,
            .xscale = 2 * lim / sz,
            .yscale = -2 * lim / sz,
            .srid = epsg,
            .epsg = epsg,
        };
    }
 
    std::generator<std::pair<tile, gil::any_image>> read(
        db::raster,
        std::vector<tile> ts) override
    {
        auto q = curl{};
        auto m = std::map<std::string, tile>{};
        for (auto& t : ts) {
            auto u = url;
            replace(u, "{z}", to_chars(t.z));
            replace(u, "{y}", to_chars(t.y));
            replace(u, "{x}", to_chars(t.x));
            q.push(u.data(), agent.data(), ssl);
            m.insert({u, t});
        }
        while (q.size()) {
            auto [u, img] = q.pop();
            co_yield {m.at(u), gil::read<boost::gil::rgba8_image_t>(img)};
        }
    }
 
    void write(db::raster const&, db::rect const&, gil::any_image_view) override
    {
        throw err;
    }
 
    void set_autocommit(bool) override { throw err; }
 
    void commit() override { throw err; }
};
 
}  // namespace boat::slippy
 
#endif  // BOAT_SLIPPY_HPP