#include <core_log.h>
#include <core_stream.h>

#ifndef __SCC_CORE_NO_MEM_PROBE_STREAM__

static int mem_probe_stream_consume(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    if (stream->curr_pos >= stream->data_length) {
        return scc_stream_eof;
    }

    unsigned char ch = stream->data[stream->curr_pos++];
    // 如果探针位置落后于当前读取位置，则更新探针位置
    if (stream->probe_pos < stream->curr_pos) {
        stream->probe_pos = stream->curr_pos;
    }
    return (int)ch;
}

static int mem_probe_stream_peek(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    if (stream->probe_pos >= stream->data_length) {
        return scc_stream_eof;
    }

    // 只查看而不移动探针位置
    return (int)(unsigned char)stream->data[stream->probe_pos];
}

static int mem_probe_stream_next(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    if (stream->probe_pos >= stream->data_length) {
        return scc_stream_eof;
    }

    // 返回探针位置的字符，并将探针位置向前移动
    int ch = (int)(unsigned char)stream->data[stream->probe_pos];
    stream->probe_pos++;
    return ch;
}

static void mem_probe_stream_sync(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    // 移动头指针到探针位置（消费已查看的字符）
    if (stream->probe_pos > stream->curr_pos) {
        stream->curr_pos = stream->probe_pos;
    }
}

static cbool mem_probe_stream_back(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    // 只能回退一个字符，且不能回退到探针位置之前
    if (stream->curr_pos == 0 || stream->curr_pos <= stream->probe_pos) {
        return false;
    }

    stream->curr_pos--;
    return true;
}

static usize mem_probe_stream_read_buf(scc_probe_stream_t *_stream,
                                       char *buffer, usize count) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    if (buffer == null) {
        LOG_WARN("Buffer is null");
        return 0;
    }

    usize remaining = stream->data_length - stream->curr_pos;
    usize to_read = (remaining < count) ? remaining : count;

    if (to_read > 0) {
        scc_memcpy(buffer, stream->data + stream->curr_pos, to_read);
        stream->curr_pos += to_read;
        // 更新探针位置
        if (stream->probe_pos < stream->curr_pos) {
            stream->probe_pos = stream->curr_pos;
        }
    } else {
        LOG_WARN("Reading past end of stream [maybe count is too large or "
                 "negative?]");
    }

    return to_read;
}

static void mem_probe_stream_reset(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    // 重置探针位置到头指针位置
    stream->probe_pos = stream->curr_pos;
}

static cbool mem_probe_stream_is_at_end(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    return stream->curr_pos >= stream->data_length;
}

static void mem_probe_stream_drop(scc_probe_stream_t *_stream) {
    Assert(_stream != null);
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;

    scc_cstring_free(&stream->stream.name);

    if (stream->owned) {
        scc_free((void *)stream->data);
        stream->data = null;
    }
}

scc_probe_stream_t *scc_mem_probe_stream_init(scc_mem_probe_stream_t *stream,
                                              const char *data, usize length,
                                              cbool owned) {
    if (stream == null || data == null) {
        LOG_ERROR("param error");
        return null;
    }

    if (length == 0) {
        LOG_WARN("input memory is empty");
        owned = false;
    }

    stream->owned = owned;
    stream->data = data;
    stream->data_length = length;
    stream->curr_pos = 0;
    stream->probe_pos = 0;

    stream->stream.name = scc_cstring_from_cstr("mem_probe_stream");

    // 设置函数指针
    stream->stream.consume = mem_probe_stream_consume;
    stream->stream.peek = mem_probe_stream_peek;
    stream->stream.next = mem_probe_stream_next;
    stream->stream.sync = mem_probe_stream_sync;
    stream->stream.back = mem_probe_stream_back;
    stream->stream.read_buf = mem_probe_stream_read_buf;
    stream->stream.reset = mem_probe_stream_reset;
    stream->stream.is_at_end = mem_probe_stream_is_at_end;
    stream->stream.drop = mem_probe_stream_drop;

    return (scc_probe_stream_t *)stream;
}

static void scc_owned_mem_stream_drop(scc_probe_stream_t *_stream) {
    scc_mem_probe_stream_t *stream = (scc_mem_probe_stream_t *)_stream;
    mem_probe_stream_drop(_stream);
    scc_free(stream);
}

scc_probe_stream_t *scc_mem_probe_stream_alloc(const char *data, usize length,
                                               cbool owned) {
    scc_mem_probe_stream_t *stream =
        (scc_mem_probe_stream_t *)scc_malloc(sizeof(scc_mem_probe_stream_t));
    if (stream == null) {
        return null;
    }

    scc_probe_stream_t *ret =
        scc_mem_probe_stream_init(stream, data, length, owned);
    stream->stream.drop = scc_owned_mem_stream_drop;
    Assert(ret != null);
    return ret;
}

#endif /* __SCC_CORE_NO_MEM_PROBE_STREAM__ */