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#include <avr/interrupt.h>

#include <avr/boot.h>

#include <avr/pgmspace.h>

#include "flash.h"

static uint16_t flash_prev_addr;

static uint8_t flash_buffer_dirty = 0;

void flash_flush_buffer() {

    uint8_t sreg;

    if (!flash_buffer_dirty) return; // Nothing to flush

    // Disable interrupts.

    sreg = SREG;

    cli();

    eeprom_busy_wait();

    boot_page_erase(flash_prev_addr);

    boot_spm_busy_wait();      // Wait until the memory is erased.

    boot_page_write(flash_prev_addr);     // Store buffer in flash page.

    boot_spm_busy_wait();       // Wait until the memory is written.

    // Reenable RWW-section again. We need this if we want to jump back

    // to the application after bootloading.

    boot_rww_enable ();

    // Re-enable interrupts (if they were ever enabled).

    SREG = sreg;

}

void flash_load_buffer(uint16_t addr) {

    //TODO: Load current flash page contents into temporary buffer to implement

    // flash read-modify-writes with word granularity. (If possible, the data

    // sheet is a little fuzzy about this.)

    uint8_t i;

    uint16_t data;

    uint16_t page = (addr / SPM_PAGESIZE) * SPM_PAGESIZE;

    for (i = 0; i < SPM_PAGESIZE; i += 2) {

        data = pgm_read_word(page + i);

        boot_page_fill(page + i, data);

    }

}

void flash_write_word(uint16_t addr, uint16_t word) {

    if ((addr / SPM_PAGESIZE) != (flash_prev_addr / SPM_PAGESIZE)) {

        flash_flush_buffer();

        flash_load_buffer(addr);

    }

    boot_page_fill(addr, word);

    flash_prev_addr = addr;

    flash_buffer_dirty = 1;

}    

void flash_init() {

    flash_prev_addr = 0xffff;

    flash_buffer_dirty = 0;

}