#include "grid.h"

#include <string.h>
#include <assert.h>

#define LOG_MODULE "grid"
#define LOG_ENABLE_DBG 0
#include "log.h"
#include "sixel.h"

#define max(x, y) ((x) > (y) ? (x) : (y))

void
grid_swap_row(struct grid *grid, int row_a, int row_b, bool initialize)
{
    assert(grid->offset >= 0);
    assert(row_a != row_b);

    int real_a = (grid->offset + row_a) & (grid->num_rows - 1);
    int real_b = (grid->offset + row_b) & (grid->num_rows - 1);

    struct row *a = grid->rows[real_a];
    struct row *b = grid->rows[real_b];

    grid->rows[real_a] = b;
    grid->rows[real_b] = a;
}

struct row *
grid_row_alloc(int cols, bool initialize)
{
    struct row *row = malloc(sizeof(*row));
    row->dirty = false;
    row->linebreak = false;

    if (initialize) {
        row->cells = calloc(cols, sizeof(row->cells[0]));
        for (size_t c = 0; c < cols; c++)
            row->cells[c].attrs.clean = 1;
    } else
        row->cells = malloc(cols * sizeof(row->cells[0]));

    return row;
}

void
grid_row_free(struct row *row)
{
    if (row == NULL)
        return;

    free(row->cells);
    free(row);
}

void
grid_reflow(struct grid *grid, int new_rows, int new_cols,
            int old_screen_rows, int new_screen_rows)
{
    struct row *const *old_grid = grid->rows;
    const int old_rows = grid->num_rows;
    const int old_cols = grid->num_cols;

    int new_col_idx = 0;
    int new_row_idx = 0;

    struct row **new_grid = calloc(new_rows, sizeof(new_grid[0]));
    struct row *new_row = new_grid[new_row_idx];

    assert(new_row == NULL);
    new_row = grid_row_alloc(new_cols, true);
    new_grid[new_row_idx] = new_row;

    /* Start at the beginning of the old grid's scrollback. That is,
     * at the output that is *oldest* */
    int offset = grid->offset + old_screen_rows;

    tll(struct sixel) new_sixels = tll_init();

    /* Turn cursor coordinates into grid absolute coordinates */
    struct coord cursor = grid->cursor.point;
    struct coord new_cursor = {};
    cursor.row += grid->offset;
    cursor.row &= old_rows - 1;

    struct coord saved_cursor = grid->saved_cursor.point;
    struct coord new_saved_cursor = {};
    saved_cursor.row += grid->offset;
    saved_cursor.row &= old_rows - 1;

    /*
     * Walk the old grid
     */
    for (int r = 0; r < old_rows; r++) {

        const size_t old_row_idx = (offset + r) & (old_rows - 1);

        /* Unallocated (empty) rows we can simply skip */
        const struct row *old_row = old_grid[old_row_idx];
        if (old_row == NULL)
            continue;

        /*
         * Update 'row' in all sixels that *begin* at current row
         *
         * Since we might end up pushing the sixel down, we can't
         * simply update the row inline - we'd then end up pushing the
         * sixel down again, when we reach the next 'old'
         * row. Instead, copy the sixel (with 'row' updated), to a
         * temporary list and remove the original sixel.
         *
         * After we've reflowed the grid we'll move the sixels back to
         * the "real" sixel list.
         */
        tll_foreach(grid->sixel_images, it) {
            if (it->item.pos.row == old_row_idx) {
                struct sixel six = it->item;
                six.pos.row = new_row_idx;

                tll_push_back(new_sixels, six);
                tll_remove(grid->sixel_images, it);
            }
        }

#define line_wrap()                                                     \
        do {                                                            \
            new_col_idx = 0;                                            \
            new_row_idx = (new_row_idx + 1) & (new_rows - 1);           \
                                                                        \
            new_row = new_grid[new_row_idx];                            \
            if (new_row == NULL) {                                      \
                new_row = grid_row_alloc(new_cols, true);               \
                new_grid[new_row_idx] = new_row;                        \
            } else {                                                    \
                memset(new_row->cells, 0, new_cols * sizeof(new_row->cells[0])); \
                new_row->linebreak = false;                             \
            }                                                           \
        } while(0)

        /*
         * Keep track of empty cells. If the old line ends with a
         * string of empty cells, we don't need to, nor do we want to,
         * add those to the new line. However, if there are non-empty
         * cells *after* the string of empty cells, we need to emit
         * the empty cells too. And that may trigger linebreaks
         */
        int empty_count = 0;

        /* Walk current line of the old grid */
        for (int c = 0; c < old_cols; c++) {
            bool has_cursor = cursor.row == old_row_idx && cursor.col == c;
            bool has_saved_cursor
                = saved_cursor.row == old_row_idx && saved_cursor.col == c;

            if (old_row->cells[c].wc == 0 && !has_cursor && !has_saved_cursor) {
                assert(!has_cursor);
                assert(!has_saved_cursor);
                empty_count++;
                continue;
            }

            int old_cols_left = old_cols - c;
            int cols_needed = empty_count + old_cols_left;
            int new_cols_left = new_cols - new_col_idx;
            if (new_cols_left < cols_needed && new_cols_left >= old_cols_left)
                empty_count = max(0, empty_count - (cols_needed - new_cols_left));

            for (int i = 0; i < empty_count + 1; i++) {
                const struct cell *old_cell = &old_row->cells[c - empty_count + i];

                /* Out of columns on current row in new grid? */
                if (new_col_idx >= new_cols) {
#if 0
                    /*
                     * If last cell on last row and first cell on new
                     * row are non-empty, wrap the line, otherwise
                     * insert a hard line break.
                     */
                    if (new_row->cells[new_cols - 1].wc == 0 ||
                        old_cell->wc == 0)
                    {
                        new_row->linebreak = true;
                    }
#endif
                    line_wrap();
                }

                assert(new_row != NULL);
                assert(new_col_idx >= 0);
                assert(new_col_idx < new_cols);

                new_row->cells[new_col_idx] = *old_cell;
                new_row->cells[new_col_idx].attrs.clean = 1;

                if (has_cursor)
                    new_cursor = (struct coord){new_col_idx, new_row_idx};
                if (has_saved_cursor)
                    new_saved_cursor = (struct coord){new_col_idx, new_row_idx};

                new_col_idx++;
            }

            empty_count = 0;
        }

        if (old_row->linebreak) {
            new_row->linebreak = true;
            line_wrap();
        }

#undef line_wrap
    }

    /* Set offset such that the last reflowed row is at the bottom */
    grid->offset = new_row_idx - new_screen_rows + 1;
    while (grid->offset < 0)
        grid->offset += new_rows;
    while (new_grid[grid->offset] == NULL)
        grid->offset = (grid->offset + 1) & (new_rows - 1);
    grid->view = grid->offset;

    /* Ensure all visible rows have been allocated */
    for (int r = 0; r < new_screen_rows; r++) {
        int idx = (grid->offset + r) & (new_rows - 1);
        if (new_grid[idx] == NULL)
            new_grid[idx] = grid_row_alloc(new_cols, true);
    }

    /* Free old grid */
    for (int r = 0; r < grid->num_rows; r++)
        grid_row_free(old_grid[r]);
    free(grid->rows);

    grid->cur_row = new_grid[new_cursor.row];
    grid->rows = new_grid;
    grid->num_rows = new_rows;
    grid->num_cols = new_cols;

    /* Convert absolute coordinates to screen relative */
    new_cursor.row -= grid->offset;
    while (new_cursor.row < 0)
        new_cursor.row += grid->num_rows;

    assert(new_cursor.row >= 0);
    assert(new_cursor.row < grid->num_rows);

    new_saved_cursor.row -= grid->offset;
    while (new_saved_cursor.row < 0)
        new_saved_cursor.row += grid->num_rows;

    assert(new_saved_cursor.row >= 0);
    assert(new_saved_cursor.row < grid->num_rows);

    grid->cursor.point = new_cursor;
    grid->saved_cursor.point = new_saved_cursor;

    grid->cursor.lcf = false;
    grid->saved_cursor.lcf = false;

    /* Destroy any non-moved sixels */
    tll_foreach(grid->sixel_images, it)
        sixel_destroy(&it->item);
    tll_free(grid->sixel_images);

    /* Move updated sixels back */
    tll_foreach(new_sixels, it)
        tll_push_back(grid->sixel_images, it->item);
    tll_free(new_sixels);
}