/**

 * Copyright (C) 2025 Niklas Haas

 *

 * This file is part of FFmpeg.

 *

 * FFmpeg is free software; you can redistribute it 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.

 *

 * FFmpeg 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

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with FFmpeg; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 */

#include "libavutil/avassert.h"

#include "libavutil/mem.h"

#include "libavutil/mem_internal.h"

#include "ops.h"

#include "ops_internal.h"

#include "ops_dispatch.h"

typedef struct SwsOpPass {

    SwsCompiledOp comp;

    SwsOpExec exec_base;

    int num_blocks;

    int tail_off_in;

    int tail_off_out;

    int tail_size_in;

    int tail_size_out;

    int planes_in;

    int planes_out;

    int pixel_bits_in;

    int pixel_bits_out;

    int idx_in[4];

    int idx_out[4];

    bool memcpy_in;

    bool memcpy_out;

} SwsOpPass;

int ff_sws_ops_compile_backend(SwsContext *ctx, const SwsOpBackend *backend,

                               const SwsOpList *ops, SwsCompiledOp *out)

{

    SwsOpList *copy;

    SwsCompiledOp compiled = {0};

    int ret = 0;

    copy = ff_sws_op_list_duplicate(ops);

    if (!copy)

        return AVERROR(ENOMEM);

    /* Ensure these are always set during compilation */

    ff_sws_op_list_update_comps(copy);

    ret = backend->compile(ctx, copy, &compiled);

    if (ret < 0) {

        int msg_lev = ret == AVERROR(ENOTSUP) ? AV_LOG_TRACE : AV_LOG_ERROR;

        av_log(ctx, msg_lev, "Backend '%s' failed to compile operations: %s\n",

               backend->name, av_err2str(ret));

    } else {

        *out = compiled;

    }

    ff_sws_op_list_free(&copy);

    return ret;

}

int ff_sws_ops_compile(SwsContext *ctx, const SwsOpList *ops, SwsCompiledOp *out)

{

    for (int n = 0; ff_sws_op_backends[n]; n++) {

        const SwsOpBackend *backend = ff_sws_op_backends[n];

        if (ops->src.hw_format != backend->hw_format ||

            ops->dst.hw_format != backend->hw_format)

            continue;

        if (ff_sws_ops_compile_backend(ctx, backend, ops, out) < 0)

            continue;

        av_log(ctx, AV_LOG_VERBOSE, "Compiled using backend '%s': "

               "block size = %d, over-read = %d, over-write = %d, cpu flags = 0x%x\n",

               backend->name, out->block_size, out->over_read, out->over_write,

               out->cpu_flags);

        ff_sws_op_list_print(ctx, AV_LOG_VERBOSE, AV_LOG_TRACE, ops);

        return 0;

    }

    av_log(ctx, AV_LOG_WARNING, "No backend found for operations:\n");

    ff_sws_op_list_print(ctx, AV_LOG_WARNING, AV_LOG_TRACE, ops);

    return AVERROR(ENOTSUP);

}

static void op_pass_free(void *ptr)

{

    SwsOpPass *p = ptr;

    if (!p)

        return;

    if (p->comp.free)

        p->comp.free(p->comp.priv);

    av_free(p);

}

static inline void get_row_data(const SwsOpPass *p, const int y,

                                const uint8_t *in[4], uint8_t *out[4])

{

    const SwsOpExec *base = &p->exec_base;

    for (int i = 0; i < p->planes_in; i++)

        in[i] = base->in[i] + (y >> base->in_sub_y[i]) * base->in_stride[i];

    for (int i = 0; i < p->planes_out; i++)

        out[i] = base->out[i] + (y >> base->out_sub_y[i]) * base->out_stride[i];

}

static void op_pass_setup(const SwsFrame *out, const SwsFrame *in,

                          const SwsPass *pass)

{

    const AVPixFmtDescriptor *indesc  = av_pix_fmt_desc_get(in->format);

    const AVPixFmtDescriptor *outdesc = av_pix_fmt_desc_get(out->format);

    SwsOpPass *p = pass->priv;

    SwsOpExec *exec = &p->exec_base;

    const SwsCompiledOp *comp = &p->comp;

    const int block_size = comp->block_size;

    p->num_blocks = (pass->width + block_size - 1) / block_size;

    /* Set up main loop parameters */

    const int aligned_w  = p->num_blocks * block_size;

    const int safe_width = (p->num_blocks - 1) * block_size;

    const int tail_size  = pass->width - safe_width;

    p->tail_off_in   = safe_width * p->pixel_bits_in  >> 3;

    p->tail_off_out  = safe_width * p->pixel_bits_out >> 3;

    p->tail_size_in  = tail_size  * p->pixel_bits_in  >> 3;

    p->tail_size_out = tail_size  * p->pixel_bits_out >> 3;

    p->memcpy_in     = false;

    p->memcpy_out    = false;

    for (int i = 0; i < p->planes_in; i++) {

        const int idx        = p->idx_in[i];

        const int chroma     = idx == 1 || idx == 2;

        const int sub_x      = chroma ? indesc->log2_chroma_w : 0;

        const int sub_y      = chroma ? indesc->log2_chroma_h : 0;

        const int plane_w    = (aligned_w + sub_x) >> sub_x;

        const int plane_pad  = (comp->over_read + sub_x) >> sub_x;

        const int plane_size = plane_w * p->pixel_bits_in >> 3;

        if (comp->slice_align)

            p->memcpy_in |= plane_size + plane_pad > in->linesize[idx];

        exec->in[i]        = in->data[idx];

        exec->in_stride[i] = in->linesize[idx];

        exec->in_sub_y[i]  = sub_y;

        exec->in_sub_x[i]  = sub_x;

    }

    for (int i = 0; i < p->planes_out; i++) {

        const int idx        = p->idx_out[i];

        const int chroma     = idx == 1 || idx == 2;

        const int sub_x      = chroma ? outdesc->log2_chroma_w : 0;

        const int sub_y      = chroma ? outdesc->log2_chroma_h : 0;

        const int plane_w    = (aligned_w + sub_x) >> sub_x;

        const int plane_pad  = (comp->over_write + sub_x) >> sub_x;

        const int plane_size = plane_w * p->pixel_bits_out >> 3;

        if (comp->slice_align)

            p->memcpy_out |= plane_size + plane_pad > out->linesize[idx];

        exec->out[i]        = out->data[idx];

        exec->out_stride[i] = out->linesize[idx];

        exec->out_sub_y[i]  = sub_y;

        exec->out_sub_x[i]  = sub_x;

    }

    /* Pre-fill pointer bump for the main section only; this value does not

     * matter at all for the tail / last row handlers because they only ever

     * process a single line */

    const int blocks_main = p->num_blocks - p->memcpy_out;

    for (int i = 0; i < 4; i++) {

        exec->in_bump[i]  = exec->in_stride[i]  - blocks_main * exec->block_size_in;

        exec->out_bump[i] = exec->out_stride[i] - blocks_main * exec->block_size_out;

    }

}

/* Dispatch kernel over the last column of the image using memcpy */

static av_always_inline void

handle_tail(const SwsOpPass *p, SwsOpExec *exec,

            const bool copy_out, const bool copy_in,

            int y, const int h)

{

    DECLARE_ALIGNED_64(uint8_t, tmp)[2][4][sizeof(uint32_t[128])];

    const SwsOpExec *base = &p->exec_base;

    const SwsCompiledOp *comp = &p->comp;

    const int tail_size_in  = p->tail_size_in;

    const int tail_size_out = p->tail_size_out;

    const int bx = p->num_blocks - 1;

    const uint8_t *in_data[4];

    uint8_t *out_data[4];

    get_row_data(p, y, in_data, out_data);

    for (int i = 0; i < p->planes_in; i++) {

        in_data[i] += p->tail_off_in;

        if (copy_in) {

            exec->in[i] = (void *) tmp[0][i];

            exec->in_stride[i] = sizeof(tmp[0][i]);

        } else {

            exec->in[i] = in_data[i];

        }

    }

    for (int i = 0; i < p->planes_out; i++) {

        out_data[i] += p->tail_off_out;

        if (copy_out) {

            exec->out[i] = (void *) tmp[1][i];

            exec->out_stride[i] = sizeof(tmp[1][i]);

        } else {

            exec->out[i] = out_data[i];

        }

    }

    for (int y_end = y + h; y < y_end; y++) {

        if (copy_in) {

            for (int i = 0; i < p->planes_in; i++) {

                av_assert2(tmp[0][i] + tail_size_in < (uint8_t *) tmp[1]);

                memcpy(tmp[0][i], in_data[i], tail_size_in);

                in_data[i] += base->in_stride[i]; /* exec->in_stride was clobbered */

            }

        }

        comp->func(exec, comp->priv, bx, y, p->num_blocks, y + 1);

        if (copy_out) {

            for (int i = 0; i < p->planes_out; i++) {

                av_assert2(tmp[1][i] + tail_size_out < (uint8_t *) tmp[2]);

                memcpy(out_data[i], tmp[1][i], tail_size_out);

                out_data[i] += base->out_stride[i];

            }

        }

        for (int i = 0; i < 4; i++) {

            if (!copy_in && exec->in[i])

                exec->in[i] += exec->in_stride[i];

            if (!copy_out && exec->out[i])

                exec->out[i] += exec->out_stride[i];

        }

    }

}

static void op_pass_run(const SwsFrame *out, const SwsFrame *in, const int y,

                        const int h, const SwsPass *pass)

{

    const SwsOpPass *p = pass->priv;

    const SwsCompiledOp *comp = &p->comp;

    /* Fill exec metadata for this slice */

    DECLARE_ALIGNED_32(SwsOpExec, exec) = p->exec_base;

    exec.slice_y = y;

    exec.slice_h = h;

    /**

     *  To ensure safety, we need to consider the following:

     *

     * 1. We can overread the input, unless this is the last line of an

     *    unpadded buffer. All defined operations can handle arbitrary pixel

     *    input, so overread of arbitrary data is fine.

     *

     * 2. We can overwrite the output, as long as we don't write more than the

     *    amount of pixels that fit into one linesize. So we always need to

     *    memcpy the last column on the output side if unpadded.

     *

     * 3. For the last row, we also need to memcpy the remainder of the input,

     *    to avoid reading past the end of the buffer. Note that since we know

     *    the run() function is called on stripes of the same buffer, we don't

     *    need to worry about this for the end of a slice.

     */

    const int last_slice  = y + h == pass->height;

    const bool memcpy_in  = last_slice && p->memcpy_in;

    const bool memcpy_out = p->memcpy_out;

    const int num_blocks  = p->num_blocks;

    const int blocks_main = num_blocks - memcpy_out;

    const int h_main      = h - memcpy_in;

    /* Handle main section */

    get_row_data(p, y, exec.in, exec.out);

    comp->func(&exec, comp->priv, 0, y, blocks_main, y + h_main);

    if (memcpy_in) {

        /* Safe part of last row */

        get_row_data(p, y + h_main, exec.in, exec.out);

        comp->func(&exec, comp->priv, 0, y + h_main, num_blocks - 1, y + h);

    }

    /* Handle last column via memcpy, takes over `exec` so call these last */

    if (memcpy_out)

        handle_tail(p, &exec, true, false, y, h_main);

    if (memcpy_in)

        handle_tail(p, &exec, memcpy_out, true, y + h_main, 1);

}

static int rw_planes(const SwsOp *op)

{

    return op->rw.packed ? 1 : op->rw.elems;

}

static int rw_pixel_bits(const SwsOp *op)

{

    const int elems = op->rw.packed ? op->rw.elems : 1;

    const int size  = ff_sws_pixel_type_size(op->type);

    const int bits  = 8 >> op->rw.frac;

    av_assert1(bits >= 1);

    return elems * size * bits;

}

static int compile(SwsGraph *graph, const SwsOpList *ops,

                   const SwsFormat *dst, SwsPass *input, SwsPass **output)

{

    SwsContext *ctx = graph->ctx;

    SwsOpPass *p = av_mallocz(sizeof(*p));

    if (!p)

        return AVERROR(ENOMEM);

    int ret = ff_sws_ops_compile(ctx, ops, &p->comp);

    if (ret < 0)

        goto fail;

    if (p->comp.opaque) {

        SwsCompiledOp c = p->comp;

        av_free(p);

        return ff_sws_graph_add_pass(graph, dst->format, dst->width, dst->height,

                                     input, c.slice_align, c.func_opaque,

                                     NULL, c.priv, c.free, output);

    }

    const SwsOp *read  = ff_sws_op_list_input(ops);

    const SwsOp *write = ff_sws_op_list_output(ops);

    p->planes_in  = rw_planes(read);

    p->planes_out = rw_planes(write);

    p->pixel_bits_in  = rw_pixel_bits(read);

    p->pixel_bits_out = rw_pixel_bits(write);

    p->exec_base = (SwsOpExec) {

        .width  = dst->width,

        .height = dst->height,

        .block_size_in  = p->comp.block_size * p->pixel_bits_in  >> 3,

        .block_size_out = p->comp.block_size * p->pixel_bits_out >> 3,

    };

    for (int i = 0; i < 4; i++) {

        p->idx_in[i]  = i < p->planes_in  ? ops->order_src.in[i] : -1;

        p->idx_out[i] = i < p->planes_out ? ops->order_dst.in[i] : -1;

    }

    return ff_sws_graph_add_pass(graph, dst->format, dst->width, dst->height,

                                 input, p->comp.slice_align, op_pass_run,

                                 op_pass_setup, p, op_pass_free, output);

fail:

    op_pass_free(p);

    return ret;

}

int ff_sws_compile_pass(SwsGraph *graph, SwsOpList *ops, int flags,

                        const SwsFormat *dst, SwsPass *input, SwsPass **output)

{

    SwsContext *ctx = graph->ctx;

    int ret;

    /* Check if the whole operation graph is an end-to-end no-op */

    if (ff_sws_op_list_is_noop(ops)) {

        *output = input;

        return 0;

    }

    const SwsOp *read  = ff_sws_op_list_input(ops);

    const SwsOp *write = ff_sws_op_list_output(ops);

    if (!read || !write) {

        av_log(ctx, AV_LOG_ERROR, "First and last operations must be a read "

               "and write, respectively.\n");

        return AVERROR(EINVAL);

    }

    if (flags & SWS_OP_FLAG_OPTIMIZE) {

        ret = ff_sws_op_list_optimize(ops);

        if (ret < 0)

            return ret;

    }

    return compile(graph, ops, dst, input, output);

}