/* 
 * This file is part of the Minecraft Overviewer.
 *
 * Minecraft Overviewer 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.
 *
 * Minecraft Overviewer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
 * Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with the Overviewer.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "overviewer.h"
#include <math.h>

/* figures out the black_coeff from a given skylight and blocklight,
   used in lighting calculations */
static float calculate_darkness(unsigned char skylight, unsigned char blocklight) {
    return 1.0f - powf(0.8f, 15.0 - MAX(blocklight, skylight));
}

/* loads the appropriate light data for the given (possibly non-local)
 * coordinates, and returns a black_coeff this is exposed, so other (derived)
 * rendermodes can use it
 *  
 * authoratative is a return slot for whether or not this lighting calculation
 * is true, or a guess. If we guessed, *authoratative will be false, but if it
 * was calculated correctly from available light data, it will be true. You
 * may (and probably should) pass NULL.
 */

inline unsigned char
estimate_blocklevel(RenderModeLighting *self, RenderState *state,
                         int x, int y, int z, int *authoratative) {

    /* placeholders for later data arrays, coordinates */
    PyObject *blocks = NULL;
    PyObject *blocklight = NULL;
    int local_x = x, local_y = y, local_z = z;
    unsigned char block, blocklevel;
    unsigned int average_count = 0, average_gather = 0, coeff = 0;

    /* defaults to "guess" until told otherwise */
    if (authoratative)
        *authoratative = 0;
    
    /* find out what chunk we're in, and translate accordingly */
    if (x >= 0 && y < 16) {
        blocks = state->blocks;
        blocklight = self->blocklight;
    } else if (x < 0) {
        local_x += 16;        
        blocks = state->left_blocks;
        blocklight = self->left_blocklight;
    } else if (y >= 16) {
        local_y -= 16;
        blocks = state->right_blocks;
        blocklight = self->right_blocklight;
    }
    
    /* make sure we have correctly-ranged coordinates */
    if (!(local_x >= 0 && local_x < 16 &&
          local_y >= 0 && local_y < 16 &&
          local_z >= 0 && local_z < 128)) {
        
        return 0;
    }

    /* also, make sure we have enough info to correctly calculate lighting */
    if (blocks == Py_None || blocks == NULL ||
        blocklight == Py_None || blocklight == NULL) {
        
        return 0;
    }

    block = getArrayByte3D(blocks, local_x, local_y, local_z);
    
    if (authoratative == NULL) {
        int auth;
        
        /* iterate through all surrounding blocks to take an average */
        int dx, dy, dz, local_block;
        for (dx = -1; dx <= 1; dx += 2) {
            for (dy = -1; dy <= 1; dy += 2) {
                for (dz = -1; dz <= 1; dz += 2) {
                    
                    /* skip if block is out of range */
                    if (x+dx < 0 || x+dx >= 16 ||
                        y+dy < 0 || y+dy >= 16 ||
                        z+dz < 0 || z+dz >= 128) {
                        continue;
                    }

                    coeff = estimate_blocklevel(self, state, x+dx, y+dy, z+dz, &auth);
                    local_block = getArrayByte3D(blocks, x+dx, y+dy, z+dz);
                    /* only add if the block is transparent, this seems to look better than
                       using every block */
                    if (auth && is_transparent(local_block)) {
                        average_gather += coeff;
                        average_count++;
                    }
                }
            }
        }
    }
    
    /* only return the average if at least one was authoratative */
    if (average_count > 0) {
        return average_gather / average_count;
    }
    
    blocklevel = getArrayByte3D(blocklight, local_x, local_y, local_z);
    
    /* no longer a guess */
    if (!(block == 44 || block == 53 || block == 67) && authoratative) {
        *authoratative = 1;
    }
    
    return blocklevel;
}

inline float
get_lighting_coefficient(RenderModeLighting *self, RenderState *state,
                         int x, int y, int z) {

    /* placeholders for later data arrays, coordinates */
    PyObject *blocks = NULL;
    PyObject *skylight = NULL;
    PyObject *blocklight = NULL;
    int local_x = x, local_y = y, local_z = z;
    unsigned char block, skylevel, blocklevel;

    /* find out what chunk we're in, and translate accordingly */
    if (x >= 0 && y < 16) {
        blocks = state->blocks;
        skylight = self->skylight;
        blocklight = self->blocklight;
    } else if (x < 0) {
        local_x += 16;        
        blocks = state->left_blocks;
        skylight = self->left_skylight;
        blocklight = self->left_blocklight;
    } else if (y >= 16) {
        local_y -= 16;
        blocks = state->right_blocks;
        skylight = self->right_skylight;
        blocklight = self->right_blocklight;
    }

    /* make sure we have correctly-ranged coordinates */
    if (!(local_x >= 0 && local_x < 16 &&
          local_y >= 0 && local_y < 16 &&
          local_z >= 0 && local_z < 128)) {
        
        return self->calculate_darkness(15, 0);
    }

    /* also, make sure we have enough info to correctly calculate lighting */
    if (blocks == Py_None || blocks == NULL ||
        skylight == Py_None || skylight == NULL ||
        blocklight == Py_None || blocklight == NULL) {
        
        return self->calculate_darkness(15, 0);
    }
    
    block = getArrayByte3D(blocks, local_x, local_y, local_z);
    skylevel = getArrayByte3D(skylight, local_x, local_y, local_z);
    blocklevel = getArrayByte3D(blocklight, local_x, local_y, local_z);

    /* special half-step handling */
    if (block == 44 || block == 53 || block == 67) {
        unsigned int upper_block;
        
        /* stairs and half-blocks take the skylevel from the upper block if it's transparent */
        if (local_z != 127) {
            int upper_counter = 0;
            /* but if the upper_block is one of these special half-steps, we need to look at *its* upper_block */
            do {
                upper_counter++; 
                upper_block = getArrayByte3D(blocks, local_x, local_y, local_z + upper_counter);
            } while ((upper_block == 44 || upper_block == 54 || upper_block == 67) && local_z < 127);
            if (is_transparent(upper_block)) {
                skylevel = getArrayByte3D(skylight, local_x, local_y, local_z + upper_counter);
            }
        } else {
            upper_block = 0;
            skylevel = 15;
        }
        
        /* the block has a bad blocklevel, estimate it from neigborhood
         * use given coordinates, no local ones! */
        blocklevel = estimate_blocklevel(self, state, x, y, z, NULL);

    }
    
    if (block == 10 || block == 11) {
        /* lava blocks should always be lit! */
        return 0.0f;
    }
    
    return self->calculate_darkness(skylevel, blocklevel);
}

/* shades the drawn block with the given facemask/black_color, based on the
   lighting results from (x, y, z) */
static inline void
do_shading_with_mask(RenderModeLighting *self, RenderState *state,
                     int x, int y, int z, PyObject *mask) {
    float black_coeff;
    
    /* first, check for occlusion if the block is in the local chunk */
    if (x >= 0 && x < 16 && y >= 0 && y < 16 && z >= 0 && z < 128) {
        unsigned char block = getArrayByte3D(state->blocks, x, y, z);
        
        if (!is_transparent(block) && !render_mode_hidden(state->rendermode, x, y, z)) {
            /* this face isn't visible, so don't draw anything */
            return;
        }
    } else if (self->skip_sides && (x == -1) && (state->left_blocks != Py_None)) {
        unsigned char block = getArrayByte3D(state->left_blocks, 15, state->y, state->z);
        if (!is_transparent(block)) {
            /* the same thing but for adjacent chunks, this solves an
               ugly black doted line between chunks in night rendermode.
               This wouldn't be necessary if the textures were truly
               tessellate-able */
               return;
           }
    } else if (self->skip_sides && (y == 16) && (state->right_blocks != Py_None)) {
        unsigned char block = getArrayByte3D(state->right_blocks, state->x, 0, state->z);
        if (!is_transparent(block)) {
            /* the same thing but for adjacent chunks, this solves an
               ugly black doted line between chunks in night rendermode.
               This wouldn't be necessary if the textures were truly
               tessellate-able */
               return;
           }
    }
    
    black_coeff = get_lighting_coefficient(self, state, x, y, z);
    black_coeff *= self->shade_strength;
    alpha_over_full(state->img, self->black_color, mask, black_coeff, state->imgx, state->imgy, 0, 0);
}

static int
rendermode_lighting_start(void *data, RenderState *state, PyObject *options) {
    RenderModeLighting* self;

    /* first, chain up */
    int ret = rendermode_normal.start(data, state, options);
    if (ret != 0)
        return ret;
    
    self = (RenderModeLighting *)data;
    
    /* skip sides by default */
    self->skip_sides = 1;

    self->shade_strength = 1.0;
    if (!render_mode_parse_option(options, "shade_strength", "f", &(self->shade_strength)))
        return 1;
    
    self->black_color = PyObject_GetAttrString(state->chunk, "black_color");
    self->facemasks_py = PyObject_GetAttrString(state->chunk, "facemasks");
    // borrowed references, don't need to be decref'd
    self->facemasks[0] = PyTuple_GetItem(self->facemasks_py, 0);
    self->facemasks[1] = PyTuple_GetItem(self->facemasks_py, 1);
    self->facemasks[2] = PyTuple_GetItem(self->facemasks_py, 2);
    
    self->skylight = PyObject_GetAttrString(state->self, "skylight");
    self->blocklight = PyObject_GetAttrString(state->self, "blocklight");
    self->left_skylight = PyObject_GetAttrString(state->self, "left_skylight");
    self->left_blocklight = PyObject_GetAttrString(state->self, "left_blocklight");
    self->right_skylight = PyObject_GetAttrString(state->self, "right_skylight");
    self->right_blocklight = PyObject_GetAttrString(state->self, "right_blocklight");
    
    self->calculate_darkness = calculate_darkness;
    
    return 0;
}

static void
rendermode_lighting_finish(void *data, RenderState *state) {
    RenderModeLighting *self = (RenderModeLighting *)data;
    
    Py_DECREF(self->black_color);
    Py_DECREF(self->facemasks_py);
    
    Py_DECREF(self->skylight);
    Py_DECREF(self->blocklight);
    Py_DECREF(self->left_skylight);
    Py_DECREF(self->left_blocklight);
    Py_DECREF(self->right_skylight);
    Py_DECREF(self->right_blocklight);
    
    /* now chain up */
    rendermode_normal.finish(data, state);
}

static int
rendermode_lighting_occluded(void *data, RenderState *state, int x, int y, int z) {
    /* no special occlusion here */
    return rendermode_normal.occluded(data, state, x, y, z);
}

static int
rendermode_lighting_hidden(void *data, RenderState *state, int x, int y, int z) {
    /* no special hiding here */
    return rendermode_normal.hidden(data, state, x, y, z);
}

static void
rendermode_lighting_draw(void *data, RenderState *state, PyObject *src, PyObject *mask, PyObject *mask_light) {
    RenderModeLighting* self;
    int x, y, z;

    /* first, chain up */
    rendermode_normal.draw(data, state, src, mask, mask_light);
    
    self = (RenderModeLighting *)data;
    x = state->x, y = state->y, z = state->z;
    
    if ((state->block == 9) || (state->block == 79)) { /* special case for water and ice */
        /* looks like we need a new case for lighting, there are
         * blocks that are transparent for occlusion calculations and
         * need per-face shading if the face is drawn. */
        if ((state->block_pdata & 16) == 16) {
            do_shading_with_mask(self, state, x, y, z+1, self->facemasks[0]);
        }
        if ((state->block_pdata & 2) == 2) { /* bottom left */
            do_shading_with_mask(self, state, x-1, y, z, self->facemasks[1]);
        }
        if ((state->block_pdata & 4) == 4) { /* bottom right */
            do_shading_with_mask(self, state, x, y+1, z, self->facemasks[2]);
        }
        /* leaves are transparent for occlusion calculations but they 
         * per face-shading to look as in game */
    } else if (is_transparent(state->block) && (state->block != 18)) {
        /* transparent: do shading on whole block */
        do_shading_with_mask(self, state, x, y, z, mask_light);
    } else {
        /* opaque: do per-face shading */
        do_shading_with_mask(self, state, x, y, z+1, self->facemasks[0]);
        do_shading_with_mask(self, state, x-1, y, z, self->facemasks[1]);
        do_shading_with_mask(self, state, x, y+1, z, self->facemasks[2]);
    }
}

const RenderModeOption rendermode_lighting_options[] = {
    {"shade_strength", "how dark to make the shadows, from 0.0 to 1.0 (default: 1.0)"},
    {NULL, NULL}
};

RenderModeInterface rendermode_lighting = {
    "lighting", "Lighting",
    "draw shadows from the lighting data",
    rendermode_lighting_options,
    &rendermode_normal,
    sizeof(RenderModeLighting),
    rendermode_lighting_start,
    rendermode_lighting_finish,
    rendermode_lighting_occluded,
    rendermode_lighting_hidden,
    rendermode_lighting_draw,
};