/*
 * This file is part of mpv.
 * Parts based on MPlayer code by Reimar Döffinger.
 *
 * mpv 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 2 of the License, or
 * (at your option) any later version.
 *
 * mpv 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 mpv.  If not, see <http://www.gnu.org/licenses/>.
 *
 * You can alternatively redistribute this file and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 */

#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include "common/common.h"
#include "gl_utils.h"

// GLU has this as gluErrorString (we don't use GLU, as it is legacy-OpenGL)
static const char *gl_error_to_string(GLenum error)
{
    switch (error) {
    case GL_INVALID_ENUM: return "INVALID_ENUM";
    case GL_INVALID_VALUE: return "INVALID_VALUE";
    case GL_INVALID_OPERATION: return "INVALID_OPERATION";
    case GL_INVALID_FRAMEBUFFER_OPERATION: return "INVALID_FRAMEBUFFER_OPERATION";
    case GL_OUT_OF_MEMORY: return "OUT_OF_MEMORY";
    default: return "unknown";
    }
}

void glCheckError(GL *gl, struct mp_log *log, const char *info)
{
    for (;;) {
        GLenum error = gl->GetError();
        if (error == GL_NO_ERROR)
            break;
        mp_msg(log, MSGL_ERR, "%s: OpenGL error %s.\n", info,
               gl_error_to_string(error));
    }
}

// return the number of bytes per pixel for the given format
// does not handle all possible variants, just those used by mpv
int glFmt2bpp(GLenum format, GLenum type)
{
    int component_size = 0;
    switch (type) {
    case GL_UNSIGNED_BYTE_3_3_2:
    case GL_UNSIGNED_BYTE_2_3_3_REV:
        return 1;
    case GL_UNSIGNED_SHORT_5_5_5_1:
    case GL_UNSIGNED_SHORT_1_5_5_5_REV:
    case GL_UNSIGNED_SHORT_5_6_5:
    case GL_UNSIGNED_SHORT_5_6_5_REV:
        return 2;
    case GL_UNSIGNED_BYTE:
        component_size = 1;
        break;
    case GL_UNSIGNED_SHORT:
        component_size = 2;
        break;
    }
    switch (format) {
    case GL_LUMINANCE:
    case GL_ALPHA:
        return component_size;
    case GL_RGB_422_APPLE:
        return 2;
    case GL_RGB:
    case GL_BGR:
    case GL_RGB_INTEGER:
        return 3 * component_size;
    case GL_RGBA:
    case GL_BGRA:
    case GL_RGBA_INTEGER:
        return 4 * component_size;
    case GL_RED:
    case GL_RED_INTEGER:
        return component_size;
    case GL_RG:
    case GL_LUMINANCE_ALPHA:
    case GL_RG_INTEGER:
        return 2 * component_size;
    }
    abort(); // unknown
}

static int get_alignment(int stride)
{
    if (stride % 8 == 0)
        return 8;
    if (stride % 4 == 0)
        return 4;
    if (stride % 2 == 0)
        return 2;
    return 1;
}

// upload a texture, handling things like stride and slices
//  target: texture target, usually GL_TEXTURE_2D
//  format, type: texture parameters
//  dataptr, stride: image data
//  x, y, width, height: part of the image to upload
//  slice: height of an upload slice, 0 for all at once
void glUploadTex(GL *gl, GLenum target, GLenum format, GLenum type,
                 const void *dataptr, int stride,
                 int x, int y, int w, int h, int slice)
{
    const uint8_t *data = dataptr;
    int y_max = y + h;
    if (w <= 0 || h <= 0)
        return;
    if (slice <= 0)
        slice = h;
    if (stride < 0) {
        data += (h - 1) * stride;
        stride = -stride;
    }
    gl->PixelStorei(GL_UNPACK_ALIGNMENT, get_alignment(stride));
    bool use_rowlength = slice > 1 && (gl->mpgl_caps & MPGL_CAP_ROW_LENGTH);
    if (use_rowlength) {
        // this is not always correct, but should work for MPlayer
        gl->PixelStorei(GL_UNPACK_ROW_LENGTH, stride / glFmt2bpp(format, type));
    } else {
        if (stride != glFmt2bpp(format, type) * w)
            slice = 1; // very inefficient, but at least it works
    }
    for (; y + slice <= y_max; y += slice) {
        gl->TexSubImage2D(target, 0, x, y, w, slice, format, type, data);
        data += stride * slice;
    }
    if (y < y_max)
        gl->TexSubImage2D(target, 0, x, y, w, y_max - y, format, type, data);
    if (use_rowlength)
        gl->PixelStorei(GL_UNPACK_ROW_LENGTH, 0);
    gl->PixelStorei(GL_UNPACK_ALIGNMENT, 4);
}

// Like glUploadTex, but upload a byte array with all elements set to val.
// If scratch is not NULL, points to a resizeable talloc memory block than can
// be freely used by the function (for avoiding temporary memory allocations).
void glClearTex(GL *gl, GLenum target, GLenum format, GLenum type,
                int x, int y, int w, int h, uint8_t val, void **scratch)
{
    int bpp = glFmt2bpp(format, type);
    int stride = w * bpp;
    int size = h * stride;
    if (size < 1)
        return;
    void *data = scratch ? *scratch : NULL;
    if (talloc_get_size(data) < size)
        data = talloc_realloc(NULL, data, char *, size);
    memset(data, val, size);
    gl->PixelStorei(GL_UNPACK_ALIGNMENT, get_alignment(stride));
    gl->TexSubImage2D(target, 0, x, y, w, h, format, type, data);
    gl->PixelStorei(GL_UNPACK_ALIGNMENT, 4);
    if (scratch) {
        *scratch = data;
    } else {
        talloc_free(data);
    }
}

mp_image_t *glGetWindowScreenshot(GL *gl)
{
    if (gl->es)
        return NULL; // ES can't read from front buffer
    GLint vp[4]; //x, y, w, h
    gl->GetIntegerv(GL_VIEWPORT, vp);
    mp_image_t *image = mp_image_alloc(IMGFMT_RGB24, vp[2], vp[3]);
    if (!image)
        return NULL;
    gl->PixelStorei(GL_PACK_ALIGNMENT, 1);
    gl->ReadBuffer(GL_FRONT);
    //flip image while reading (and also avoid stride-related trouble)
    for (int y = 0; y < vp[3]; y++) {
        gl->ReadPixels(vp[0], vp[1] + vp[3] - y - 1, vp[2], 1,
                       GL_RGB, GL_UNSIGNED_BYTE,
                       image->planes[0] + y * image->stride[0]);
    }
    gl->PixelStorei(GL_PACK_ALIGNMENT, 4);
    return image;
}

void mp_log_source(struct mp_log *log, int lev, const char *src)
{
    int line = 1;
    if (!src)
        return;
    while (*src) {
        const char *end = strchr(src, '\n');
        const char *next = end + 1;
        if (!end)
            next = end = src + strlen(src);
        mp_msg(log, lev, "[%3d] %.*s\n", line, (int)(end - src), src);
        line++;
        src = next;
    }
}

static void gl_vao_enable_attribs(struct gl_vao *vao)
{
    GL *gl = vao->gl;

    for (int n = 0; vao->entries[n].name; n++) {
        const struct gl_vao_entry *e = &vao->entries[n];

        gl->EnableVertexAttribArray(n);
        gl->VertexAttribPointer(n, e->num_elems, e->type, e->normalized,
                                vao->stride, (void *)(intptr_t)e->offset);
    }
}

void gl_vao_init(struct gl_vao *vao, GL *gl, int stride,
                 const struct gl_vao_entry *entries)
{
    assert(!vao->vao);
    assert(!vao->buffer);

    *vao = (struct gl_vao){
        .gl = gl,
        .stride = stride,
        .entries = entries,
    };

    gl->GenBuffers(1, &vao->buffer);

    if (gl->BindVertexArray) {
        gl->BindBuffer(GL_ARRAY_BUFFER, vao->buffer);

        gl->GenVertexArrays(1, &vao->vao);
        gl->BindVertexArray(vao->vao);
        gl_vao_enable_attribs(vao);
        gl->BindVertexArray(0);

        gl->BindBuffer(GL_ARRAY_BUFFER, 0);
    }
}

void gl_vao_uninit(struct gl_vao *vao)
{
    GL *gl = vao->gl;
    if (!gl)
        return;

    if (gl->DeleteVertexArrays)
        gl->DeleteVertexArrays(1, &vao->vao);
    gl->DeleteBuffers(1, &vao->buffer);

    *vao = (struct gl_vao){0};
}

void gl_vao_bind(struct gl_vao *vao)
{
    GL *gl = vao->gl;

    if (gl->BindVertexArray) {
        gl->BindVertexArray(vao->vao);
    } else {
        gl->BindBuffer(GL_ARRAY_BUFFER, vao->buffer);
        gl_vao_enable_attribs(vao);
        gl->BindBuffer(GL_ARRAY_BUFFER, 0);
    }
}

void gl_vao_unbind(struct gl_vao *vao)
{
    GL *gl = vao->gl;

    if (gl->BindVertexArray) {
        gl->BindVertexArray(0);
    } else {
        for (int n = 0; vao->entries[n].name; n++)
            gl->DisableVertexAttribArray(n);
    }
}

void gl_vao_bind_attribs(struct gl_vao *vao, GLuint program)
{
    GL *gl = vao->gl;

    for (int n = 0; vao->entries[n].name; n++)
        gl->BindAttribLocation(program, n, vao->entries[n].name);
}

// Draw the vertex data (as described by the gl_vao_entry entries) in ptr
// to the screen. num is the number of vertexes. prim is usually GL_TRIANGLES.
// If ptr is NULL, then skip the upload, and use the data uploaded with the
// previous call.
void gl_vao_draw_data(struct gl_vao *vao, GLenum prim, void *ptr, size_t num)
{
    GL *gl = vao->gl;

    if (ptr) {
        gl->BindBuffer(GL_ARRAY_BUFFER, vao->buffer);
        gl->BufferData(GL_ARRAY_BUFFER, num * vao->stride, ptr, GL_DYNAMIC_DRAW);
        gl->BindBuffer(GL_ARRAY_BUFFER, 0);
    }

    gl_vao_bind(vao);

    gl->DrawArrays(prim, 0, num);

    gl_vao_unbind(vao);
}

// Create a texture and a FBO using the texture as color attachments.
//  gl_target: GL_TEXTURE_2D
//  gl_filter: GL_LINEAR
//  iformat: texture internal format
// Returns success.
bool fbotex_init(struct fbotex *fbo, GL *gl, struct mp_log *log, int w, int h,
                 GLenum gl_target, GLenum gl_filter, GLenum iformat)
{
    bool res = true;

    assert(!fbo->fbo);
    assert(!fbo->texture);

    *fbo = (struct fbotex) {
        .gl = gl,
        .vp_w = w,
        .vp_h = h,
        .tex_w = w,
        .tex_h = h,
    };

    mp_verbose(log, "Create FBO: %dx%d\n", fbo->tex_w, fbo->tex_h);

    if (!(gl->mpgl_caps & MPGL_CAP_FB))
        return false;

    gl->GenFramebuffers(1, &fbo->fbo);
    gl->GenTextures(1, &fbo->texture);
    gl->BindTexture(gl_target, fbo->texture);
    gl->TexImage2D(gl_target, 0, iformat, fbo->tex_w, fbo->tex_h, 0,
                   GL_RGBA, GL_UNSIGNED_BYTE, NULL);
    gl->TexParameteri(gl_target, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    gl->TexParameteri(gl_target, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    gl->TexParameteri(gl_target, GL_TEXTURE_MIN_FILTER, gl_filter);
    gl->TexParameteri(gl_target, GL_TEXTURE_MAG_FILTER, gl_filter);

    glCheckError(gl, log, "after creating framebuffer texture");

    gl->BindFramebuffer(GL_FRAMEBUFFER, fbo->fbo);
    gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                             gl_target, fbo->texture, 0);

    GLenum err = gl->CheckFramebufferStatus(GL_FRAMEBUFFER);
    if (err != GL_FRAMEBUFFER_COMPLETE) {
        mp_err(log, "Error: framebuffer completeness check failed (error=%d).\n",
               (int)err);
        res = false;
    }

    gl->BindFramebuffer(GL_FRAMEBUFFER, 0);

    glCheckError(gl, log, "after creating framebuffer");

    return res;
}

void fbotex_uninit(struct fbotex *fbo)
{
    GL *gl = fbo->gl;

    if (gl && (gl->mpgl_caps & MPGL_CAP_FB)) {
        gl->DeleteFramebuffers(1, &fbo->fbo);
        gl->DeleteTextures(1, &fbo->texture);
        *fbo = (struct fbotex) {0};
    }
}

void gl_matrix_ortho2d(float m[3][3], float x0, float x1, float y0, float y1)
{
    memset(m, 0, 9 * sizeof(float));
    m[0][0] = 2.0f / (x1 - x0);
    m[1][1] = 2.0f / (y1 - y0);
    m[2][0] = -(x1 + x0) / (x1 - x0);
    m[2][1] = -(y1 + y0) / (y1 - y0);
    m[2][2] = 1.0f;
}

static void GLAPIENTRY gl_debug_cb(GLenum source, GLenum type, GLuint id,
                                   GLenum severity, GLsizei length,
                                   const GLchar *message, const void *userParam)
{
    // keep in mind that the debug callback can be asynchronous
    struct mp_log *log = (void *)userParam;
    int level = MSGL_ERR;
    switch (severity) {
    case GL_DEBUG_SEVERITY_NOTIFICATION:level = MSGL_V; break;
    case GL_DEBUG_SEVERITY_LOW:         level = MSGL_INFO; break;
    case GL_DEBUG_SEVERITY_MEDIUM:      level = MSGL_WARN; break;
    case GL_DEBUG_SEVERITY_HIGH:        level = MSGL_ERR; break;
    }
    mp_msg(log, level, "GL: %s\n", message);
}

void gl_set_debug_logger(GL *gl, struct mp_log *log)
{
    if (gl->DebugMessageCallback) {
        if (log) {
            gl->DebugMessageCallback(gl_debug_cb, log);
        } else {
            gl->DebugMessageCallback(NULL, NULL);
        }
    }
}