/* I²C 的假实现：一张寄存器表 + 可注入的 NAK。宿主机专用。 */
#include <assert.h>
#include <string.h>

#include "sim_hal.h"

static sim_i2c_dev_t s_dev[SIM_I2C_MAX_DEV];
static int           s_n;
static bool          s_inited;

void sim_i2c_reset_internal(void); /* 只给 sim_hal_reset() 用 */

void sim_i2c_reset_internal(void)
{
    memset(s_dev, 0, sizeof(s_dev));
    s_n = 0;
    s_inited = false;
}

sim_i2c_dev_t *sim_i2c_dev(uint8_t addr)
{
    for (int i = 0; i < s_n; i++) {
        if (s_dev[i].addr == addr) {
            return &s_dev[i];
        }
    }
    return NULL;
}

sim_i2c_dev_t *sim_i2c_add(uint8_t addr, uint8_t reg_width)
{
    assert(addr <= 0x7f);
    assert(reg_width == 1 || reg_width == 2);
    assert(sim_i2c_dev(addr) == NULL); /* 地址撞车：测试写错了 */
    assert(s_n < SIM_I2C_MAX_DEV);

    sim_i2c_dev_t *d = &s_dev[s_n++];
    memset(d, 0, sizeof(*d));
    d->addr = addr;
    d->reg_width = reg_width;
    d->present = true;
    return d;
}

static sim_i2c_dev_t *must(uint8_t addr)
{
    sim_i2c_dev_t *d = sim_i2c_dev(addr);
    assert(d != NULL); /* 先 sim_i2c_add() 再预置寄存器 */
    return d;
}

void sim_i2c_set_reg(uint8_t addr, uint8_t reg, uint16_t val) { must(addr)->regs[reg] = val; }
uint16_t sim_i2c_get_reg(uint8_t addr, uint8_t reg) { return must(addr)->regs[reg]; }
void sim_i2c_inject_nak(uint8_t addr, int count) { must(addr)->nak_left = count; }
void sim_i2c_set_present(uint8_t addr, bool present) { must(addr)->present = present; }

/* ---- HAL 实现 ---------------------------------------------------------- */

hal_err_t hal_i2c_init(const hal_i2c_cfg_t *cfg)
{
    (void)cfg; /* sim 不关心引脚与速率 */
    s_inited = true;
    return HAL_OK;
}

/* 取器件并把「这次事务要不要 NAK」判掉。 */
static hal_err_t take(uint8_t addr, sim_i2c_dev_t **out)
{
    if (!s_inited) {
        return HAL_ERR_STATE;
    }
    if (addr > 0x7f) {
        return HAL_ERR_ARG;
    }
    sim_i2c_dev_t *d = sim_i2c_dev(addr);
    if (d == NULL || !d->present) {
        return HAL_ERR_NAK;
    }
    if (d->nak_left != 0) {
        if (d->nak_left > 0) {
            d->nak_left--;
        }
        return HAL_ERR_NAK;
    }
    *out = d;
    return HAL_OK;
}

/* data[0] 是寄存器指针，其后按 reg_width 一格一格写，指针自增（uint8_t 自然回绕）。 */
static hal_err_t do_write(sim_i2c_dev_t *d, const uint8_t *data, size_t len)
{
    if (len != 0 && data == NULL) {
        return HAL_ERR_ARG;
    }
    if (len > 1 && ((len - 1) % d->reg_width) != 0) {
        return HAL_ERR_ARG; /* 半个寄存器：真器件上是未定义行为，这里直接报错 */
    }
    d->n_write++;
    d->last_write_len = (uint8_t)(len < SIM_I2C_LOG_BYTES ? len : SIM_I2C_LOG_BYTES);
    if (d->last_write_len != 0) {
        memcpy(d->last_write, data, d->last_write_len);
    }
    if (len == 0) {
        return HAL_OK; /* 只发地址 = 探测 */
    }
    d->ptr = data[0];
    for (size_t i = 1; i < len; i += d->reg_width) {
        uint16_t v = data[i];
        if (d->reg_width == 2) {
            v = (uint16_t)((v << 8) | data[i + 1]);
        }
        d->regs[d->ptr++] = v;
    }
    return HAL_OK;
}

static hal_err_t do_read(sim_i2c_dev_t *d, uint8_t *data, size_t len)
{
    if (len != 0 && data == NULL) {
        return HAL_ERR_ARG;
    }
    if ((len % d->reg_width) != 0) {
        return HAL_ERR_ARG;
    }
    d->n_read++;
    for (size_t i = 0; i < len; i += d->reg_width) {
        uint16_t v = d->regs[d->ptr++];
        if (d->reg_width == 2) {
            data[i] = (uint8_t)(v >> 8);
            data[i + 1] = (uint8_t)(v & 0xff);
        } else {
            data[i] = (uint8_t)v;
        }
    }
    return HAL_OK;
}

hal_err_t hal_i2c_write(uint8_t addr, const uint8_t *data, size_t len)
{
    sim_i2c_dev_t *d = NULL;
    hal_err_t err = take(addr, &d);
    return err != HAL_OK ? err : do_write(d, data, len);
}

hal_err_t hal_i2c_read(uint8_t addr, uint8_t *data, size_t len)
{
    sim_i2c_dev_t *d = NULL;
    hal_err_t err = take(addr, &d);
    return err != HAL_OK ? err : do_read(d, data, len);
}

hal_err_t hal_i2c_write_read(uint8_t addr, const uint8_t *wr, size_t wr_len,
                             uint8_t *rd, size_t rd_len)
{
    sim_i2c_dev_t *d = NULL;
    hal_err_t err = take(addr, &d);
    if (err != HAL_OK) {
        return err;
    }
    err = do_write(d, wr, wr_len);
    return err != HAL_OK ? err : do_read(d, rd, rd_len);
}

hal_err_t hal_i2c_probe(uint8_t addr)
{
    sim_i2c_dev_t *d = NULL;
    return take(addr, &d);
}