---------------------------------------------------------------------------
-- Voxelis - Voxel survival sandbox for Luanti
-- Copyright (C) 2024 Mad Star Studio LLC
-- 
-- This program is free software; you can redistribute it and/or modify
-- it under the terms of the GNU General Public License as published by
-- the Free Software Foundation; either version 3 of the License, or
-- (at your option) any later version.
--
-- You should have received a copy of the GNU General Public License along
-- with this program; if not, see <http://www.gnu.org/licenses/>.
---------------------------------------------------------------------------

vox_mapgen_core = {}

-- -------------------------------------------------------------- --
-- Configuration: Noise Parameters
-- -------------------------------------------------------------- --
local noise_heat = {
    offset = 50,
    scale = 50,
    spread = {x = 1000, y = 1000, z = 1000},
    seed = 1234,
    octaves = 3,
    persistence = 0.5,
    lacunarity = 2.0,
}

local noise_humidity = {
    offset = 50,
    scale = 50,
    spread = {x = 1000, y = 1000, z = 1000},
    seed = 5678,
    octaves = 3,
    persistence = 0.5,
    lacunarity = 2.0,
}

local noise_altitude = {
    offset = 50,
    scale = 50,
    spread = {x = 1000, y = 1000, z = 1000},
    seed = 91011,
    octaves = 3,
    persistence = 0.5,
    lacunarity = 2.0,
}

local biome_size_noise = {
    offset = 0,
    scale = 10,
    spread = {x = 2000, y = 2000, z = 2000},
    seed = 78910,
    octaves = 2,
    persistence = 0.4,
    lacunarity = 2.0,
}

-- Apply noise parameters to the map generator
minetest.register_on_mapgen_init(function(mapgen_params)
    minetest.set_mapgen_setting_noiseparams("heat", noise_heat, true)
    minetest.set_mapgen_setting_noiseparams("humidity", noise_humidity, true)
    minetest.set_mapgen_setting_noiseparams("altitude", noise_altitude, true)
end)

-- -------------------------------------------------------------- --
-- Biome Assignment Logic
-- -------------------------------------------------------------- --
local function get_biome(heat, humidity, altitude)
    if heat > 70 and humidity < 30 then
        return "desert"
    elseif heat > 70 and humidity > 50 then
        if altitude > 100 then
            return "volcanic_fields"
        end
        return "savannah"
    elseif heat > 50 and humidity > 70 then
        return "tropical_rainforest"
    elseif heat < 30 and humidity > 60 then
        return "boreal_forest"
    elseif heat < 10 and humidity > 40 then
        return "frozen_tundra"
    elseif altitude > 256 then
        return "jade_cliffs"
    else
        return "grassland" -- Default biome
    end
end

local function blend_biomes(current_biome, neighbor_biome, distance)
    if distance < 10 and math.random() < 0.5 then
        return neighbor_biome
    end
    return current_biome
end

-- -------------------------------------------------------------- --
-- Map Generation Logic
-- -------------------------------------------------------------- --

minetest.register_on_generated(function(minp, maxp, seed)
    local vm, emin, emax = minetest.get_mapgen_object("voxelmanip")
    local area = VoxelArea:new{MinEdge = emin, MaxEdge = emax}
    local data = vm:get_data()

    -- Generate noise maps
    local heat_map = minetest.get_perlin_map(noise_heat, {x = maxp.x - minp.x + 1, y = maxp.z - minp.z + 1})
    local humidity_map = minetest.get_perlin_map(noise_humidity, {x = maxp.x - minp.x + 1, y = maxp.z - minp.z + 1})
    local altitude_map = minetest.get_perlin_map(noise_altitude, {x = maxp.x - minp.x + 1, y = maxp.z - minp.z + 1})
    local biome_size_map = minetest.get_perlin_map(biome_size_noise, {x = maxp.x - minp.x + 1, y = maxp.z - minp.z + 1})

    local heat = heat_map:get_2d_map_flat({x = minp.x, y = minp.z})
    local humidity = humidity_map:get_2d_map_flat({x = minp.x, y = minp.z})
    local altitude = altitude_map:get_2d_map_flat({x = minp.x, y = minp.z})
    local biome_sizes = biome_size_map:get_2d_map_flat({x = minp.x, y = minp.z})

    for z = minp.z, maxp.z do
        for x = minp.x, maxp.x do
            local index2d = (z - minp.z) * (maxp.x - minp.x + 1) + (x - minp.x + 1)
            local h = heat[index2d]
            local hum = humidity[index2d]
            local alt = altitude[index2d]
            local biome_size = biome_sizes[index2d]

            local current_biome = get_biome(h, hum, alt)
            local neighbor_biome = get_biome(h + 5, hum + 5, alt)
            current_biome = blend_biomes(current_biome, neighbor_biome, biome_size)

            -- Fetch biome properties
            local node_top = core.get_biome_top_node(current_biome) or "vox_worldblocks:grass"
            local node_filler = core.get_biome_filler_node(current_biome) or "vox_worldblocks:dirt"
            local depth_top = core.get_biome_depth_top(current_biome) or 1
            local depth_filler = core.get_biome_depth_filler(current_biome) or 3

            for y = minp.y, maxp.y do
                local vi = area:index(x, y, z)

                if y == minp.y then
                    data[vi] = minetest.get_content_id("vox_worldblocks:bedrock")
                elseif y < -10001 then
                    data[vi] = minetest.get_content_id("air")
                elseif y <= minp.y + depth_top then
                    data[vi] = minetest.get_content_id(node_top)
                elseif y <= minp.y + depth_top + depth_filler then
                    data[vi] = minetest.get_content_id(node_filler)
                else
                    data[vi] = minetest.get_content_id("air")
                end
            end
        end
    end

    vm:set_data(data)
    vm:write_to_map()
end)