/**
 * TODO file description
 */

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


/** Initialize the struct */
void LcdBuffer_Init(struct LcdBuffer *self, const struct cgrom_entry *cgrom, const struct cgram_pattern *custom_symbols)
{
    assert(self);
    assert(cgrom);
    assert(custom_symbols);

    LcdBuffer_Clear(self);
    self->cgrom = cgrom;
    self->custom_symbols = custom_symbols;
}

/** Clear the screen */
void LcdBuffer_Clear(struct LcdBuffer *self)
{
    assert(self);

    memset(self->cgram, 0, sizeof(self->cgram));
    memset(self->screen, 32, sizeof(self->screen));
    memset(self->dirty_extents, 0, sizeof(self->dirty_extents));
    self->full_repaint_required = false;
}

/** Write what needs to be written to the HW, clear all dirty marks */
void LcdBuffer_Flush(struct LcdBuffer *self)
{
    for (int i = 0; i < 8; i++) {
        if (self->cgram[i].refcount > 0 && self->cgram[i].dirty) {
            LcdBuffer_IO_WriteCGRAM(i, self->custom_symbols[self->cgram[i].symbol_index].data);
            self->cgram[i].dirty = false;
        }
    }

    if (self->full_repaint_required) {
        for (int r = 0; r < LINE_NUM; r++) {
            LcdBuffer_IO_WriteAt(r, 0, self->screen[r], LINE_LEN);
        }
        memset(self->dirty_extents, 0, sizeof(self->dirty_extents));
    } else {
        for (int e = 0; e < BUFLEN_DIRTY_LIST; e++) {
            struct DirtyExtent *ext = &self->dirty_extents[e];
            if (!ext->count) {
                continue;
            }
            LcdBuffer_IO_WriteAt(ext->row, ext->col, &self->screen[ext->row][ext->col], ext->count);
            ext->count = 0; // mark the slot as free
        }
    }
}

/** Fully write everything to the display */
void LcdBuffer_FlushAll(struct LcdBuffer *self)
{
    for (int i = 0; i < 8; i++) {
        if (self->cgram[i].refcount > 0) {
            LcdBuffer_IO_WriteCGRAM(i, self->custom_symbols[self->cgram[i].symbol_index].data);
        }
        self->cgram[i].dirty = false;
    }

    for (int r = 0; r < LINE_NUM; r++) {
        LcdBuffer_IO_WriteAt(r, 0, self->screen[r], LINE_LEN);
    }

    memset(self->dirty_extents, 0, sizeof(self->dirty_extents));
    self->full_repaint_required = false;
}

static void mark_dirty(struct LcdBuffer *self, uint8_t row, uint8_t col)
{
    int first_empty_extent_slot = -1;
    for (int i = 0; i < BUFLEN_DIRTY_LIST; i++) {
        struct DirtyExtent *ext = &self->dirty_extents[i];
        if (ext->count == 0) {
            // unused
            if (first_empty_extent_slot == -1) {
                first_empty_extent_slot = i;
            }
            continue;
        }
        if (ext->row != row) {
            // not this row
            continue;
        }

        // this is a filled extent

        if (ext->col < col && ext->col + ext->count > col) {
            // already in this extent
            return;
        }

        if (col < ext->col && (ext->col - col) <= 5) {
            ext->count += (ext->col - col);
            ext->col = col;
            return;
        }

        if (col >= ext->col + ext->count && (col - ext->col + ext->count) <= 5) {
            ext->count += (col - ext->col + ext->count);
            return;
        }
    }

    if (first_empty_extent_slot == -1) {
        self->full_repaint_required = true;
    } else {
        self->dirty_extents[first_empty_extent_slot].col = col;
        self->dirty_extents[first_empty_extent_slot].row = row;
        self->dirty_extents[first_empty_extent_slot].count = 1;
    }
}

/** Set one utf8 character at a position */
void LcdBuffer_Set(struct LcdBuffer *self, uint8_t row, uint8_t col, struct Utf8Char ch)
{
    assert(self);
    assert(row < LINE_NUM);
    assert(col < LINE_LEN);

    uint8_t oldchar = self->screen[row][col];

    if (oldchar >= 8 && oldchar == ch.uint) {
        // No change
        return;
    }

    // Fast path for standard ASCII
    if (ch.uint >= 32 && ch.uint < 126 && ch.uint != '\\') { // A00 has YEN in place of BACKSLASH
        // normal ASCII
        if (oldchar < 8) {
            // release refcount on the CGRAM cell
            self->cgram[oldchar].refcount -= 1;
        }

        self->screen[row][col] = ch.uint;
        goto done_dirty;
    }

    // Find if it's in CGROM
    const struct cgrom_entry *rom = self->cgrom;
    for (;;) {
        if (rom->symbol.uint == 0) {
            // End of the lookup table
            break;
        }

        if (rom->symbol.uint == ch.uint) {
            // found it!
            if (oldchar < 8) {
                // release refcount on the CGRAM cell
                self->cgram[oldchar].refcount -= 1;
            }

            self->screen[row][col] = rom->address;
            goto done_dirty;
        }

        rom++;
    }

    // Check if the same custom char is already used - if so, increment refcount and reuse it
    int first_empty_custom_slot = -1;
    for (int i = 0; i < 8; i++) {
        if (self->cgram[i].refcount > 0) {
            if (self->cgram[i].uint == ch.uint) {
                if (oldchar == i) {
                    // No change, was already the same custom
                    return;
                }

                if (oldchar < 8) {
                    // release refcount on the CGRAM cell
                    self->cgram[oldchar].refcount -= 1;
                }

                self->cgram[i].refcount += 1;
                self->screen[row][col] = i;
                goto done_dirty;
            }
        } else if (first_empty_custom_slot == -1) {
            first_empty_custom_slot = i;
        }
    }

    // New custom pattern is needed

    if (oldchar < 8) {
        // release refcount on the CGRAM cell
        self->cgram[oldchar].refcount -= 1;
    }

    uint32_t index = 0;
    const struct cgram_pattern *pattern = self->custom_symbols;
    for (;;) {
        if (pattern->symbol.uint == 0) {
            // End of the lookup table
            break;
        }

        if (pattern->symbol.uint == ch.uint) {
            // found it!

            if (first_empty_custom_slot == -1) {
                // Whoops, out of slots. Show a fallback glyph
                if (oldchar != pattern->fallback) {
                    self->screen[row][col] = pattern->fallback;
                    goto done_dirty;
                }
                return;
            }

            // Allocate a new slot in the CGRAM
            self->cgram[first_empty_custom_slot].refcount = 1;
            self->cgram[first_empty_custom_slot].uint = ch.uint;
            self->cgram[first_empty_custom_slot].dirty = true; // it should be flushed!
            self->cgram[first_empty_custom_slot].symbol_index = index;

            self->screen[row][col] = first_empty_custom_slot;
            goto done_dirty;
        }

        index++;
        pattern++;
    }

    // Fallback, no way to show this glyph
    self->screen[row][col] = '?';

    done_dirty:
    mark_dirty(self, row, col);
}

/** Write a UTF8 string at a position */
void LcdBuffer_Write(struct LcdBuffer *self, uint8_t row, uint8_t col, char *utf_string)
{
    struct Utf8Iterator iter;
    Utf8Iterator_Init(&iter, utf_string);
    struct Utf8Char uchar;
    while ((uchar = Utf8Iterator_Next(&iter)).uint) {
        if (col >= LINE_LEN) {
            break;
        }
        LcdBuffer_Set(self, row, col, uchar);
        col++;
    }
}