/*
 * Copyright (c) 2017 Richard Braun.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <assert.h>
#include <limits.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdint.h>

#include <kern/cbuf.h>
#include <kern/init.h>
#include <kern/log.h>
#include <kern/macros.h>
#include <kern/panic.h>
#include <kern/spinlock.h>
#include <kern/thread.h>

#define LOG_BUFFER_SIZE 16384

#if !ISP2(LOG_BUFFER_SIZE)
#error "log buffer size must be a power-of-two"
#endif

#define LOG_MSG_SIZE 128

#define LOG_MARKER 0x1

static struct thread *log_thread;

static struct cbuf log_cbuf;
static char log_buffer[LOG_BUFFER_SIZE];

static unsigned long log_nr_overruns;

static unsigned int log_print_level;

/*
 * Global lock.
 *
 * Interrupts must be disabled when holding this lock.
 */
static struct spinlock log_lock;

/*
 * A record starts with a marker byte and ends with a null terminating byte.
 *
 * There must be no null byte inside the header, and the buffer is expected
 * to be a standard null-terminated string.
 */
struct log_record {
    uint8_t mark;
    uint8_t level;
    char buffer[LOG_MSG_SIZE];
};

static void
log_push(char c)
{
    if (cbuf_size(&log_cbuf) == cbuf_capacity(&log_cbuf)) {
        log_nr_overruns++;
    }

    cbuf_push(&log_cbuf, c);
}

static const char *
log_level2str(unsigned int level)
{
    switch (level) {
    case LOG_EMERG:
        return "emerg";
    case LOG_ALERT:
        return "alert";
    case LOG_CRIT:
        return "crit";
    case LOG_ERR:
        return "error";
    case LOG_WARNING:
        return "warning";
    case LOG_NOTICE:
        return "notice";
    case LOG_INFO:
        return "info";
    case LOG_DEBUG:
        return "debug";
    default:
        return NULL;
    }
}

static char
log_level2char(unsigned int level)
{
    assert(level < LOG_NR_LEVELS);
    return '0' + level;
}

static uint8_t
log_char2level(char c)
{
    uint8_t level;

    level = c - '0';
    assert(level < LOG_NR_LEVELS);
    return level;
}

static void
log_record_init_produce(struct log_record *record, unsigned int level)
{
    record->mark = LOG_MARKER;
    record->level = log_level2char(level);
}

static void
log_record_consume(struct log_record *record, char c, size_t *sizep)
{
    char *ptr;

    assert(*sizep < sizeof(*record));

    ptr = (char *)record;
    ptr[*sizep] = c;
    (*sizep)++;
}

static int
log_record_init_consume(struct log_record *record)
{
    bool marker_found;
    size_t size;
    int error;
    char c;

    marker_found = false;
    size = 0;

    for (;;) {
        error = cbuf_pop(&log_cbuf, &c);

        if (error) {
            if (!marker_found) {
                return ERROR_INVAL;
            }

            break;
        }

        if (!marker_found) {
            if (c != LOG_MARKER) {
                continue;
            }

            marker_found = true;
            log_record_consume(record, c, &size);
            continue;
        } else if (size == offsetof(struct log_record, level)) {
            record->level = log_char2level(c);
            size++;
            continue;
        }

        log_record_consume(record, c, &size);

        if (c == '\0') {
            break;
        }
    }

    return 0;
}

static void
log_record_print(const struct log_record *record)
{
    if (record->level > log_print_level) {
        return;
    }

    if (record->level <= LOG_WARNING) {
        printf("%7s %s\n", log_level2str(record->level), record->buffer);
    } else {
        printf("%s\n", record->buffer);
    }
}

static void
log_record_push(struct log_record *record)
{
    const char *ptr;

    ptr = (const char *)record;

    while (*ptr != '\0') {
        log_push(*ptr);
        ptr++;
    }

    log_push('\0');
}

static void
log_run(void *arg)
{
    unsigned long flags, nr_overruns;
    struct log_record record;
    int error;

    (void)arg;

    nr_overruns = 0;

    for (;;) {
        spinlock_lock_intr_save(&log_lock, &flags);

        while (cbuf_size(&log_cbuf) == 0) {
            thread_sleep(&log_lock, &log_cbuf, "log_cbuf");
        }

        error = log_record_init_consume(&record);

        /* Drain the log buffer before reporting overruns */
        if (cbuf_size(&log_cbuf) == 0) {
            nr_overruns = log_nr_overruns;
            log_nr_overruns = 0;
        }

        spinlock_unlock_intr_restore(&log_lock, flags);

        if (!error) {
            log_record_print(&record);
        }

        if (nr_overruns != 0) {
            log_msg(LOG_ERR, "log: buffer overruns, %lu bytes dropped",
                    nr_overruns);
            nr_overruns = 0;
        }
    }
}

void __init
log_setup(void)
{
    cbuf_init(&log_cbuf, log_buffer, sizeof(log_buffer));
    spinlock_init(&log_lock);
    log_print_level = LOG_INFO;
}

void __init
log_start(void)
{
    struct thread_attr attr;
    int error;

    thread_attr_init(&attr, THREAD_KERNEL_PREFIX "log_run");
    thread_attr_set_detached(&attr);
    error = thread_create(&log_thread, &attr, log_run, NULL);

    if (error) {
        panic("log: unable to create thread");
    }
}

int
log_msg(unsigned int level, const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_vmsg(level, format, ap);
    va_end(ap);

    return ret;
}

int
log_vmsg(unsigned int level, const char *format, va_list ap)
{
    struct log_record record;
    unsigned long flags;
    int nr_chars;

    log_record_init_produce(&record, level);
    nr_chars = vsnprintf(record.buffer, sizeof(record.buffer), format, ap);

    if ((unsigned int)nr_chars >= sizeof(record.buffer)) {
        log_msg(LOG_ERR, "log: message too large");
        goto out;;
    }

    spinlock_lock_intr_save(&log_lock, &flags);
    log_record_push(&record);
    thread_wakeup(log_thread);
    spinlock_unlock_intr_restore(&log_lock, flags);

out:
    return nr_chars;
}

int
log_emerg(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_vemerg(format, ap);
    va_end(ap);

    return ret;
}

int
log_alert(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_valert(format, ap);
    va_end(ap);

    return ret;
}

int
log_crit(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_vcrit(format, ap);
    va_end(ap);

    return ret;
}

int
log_err(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_verr(format, ap);
    va_end(ap);

    return ret;
}

int
log_warning(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_vwarning(format, ap);
    va_end(ap);

    return ret;
}

int
log_notice(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_vnotice(format, ap);
    va_end(ap);

    return ret;
}

int
log_info(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_vinfo(format, ap);
    va_end(ap);

    return ret;
}

int
log_debug(const char *format, ...)
{
    va_list ap;
    int ret;

    va_start(ap, format);
    ret = log_vdebug(format, ap);
    va_end(ap);

    return ret;
}

int
log_vemerg(const char *format, va_list ap)
{
    return log_vmsg(LOG_EMERG, format, ap);
}

int
log_valert(const char *format, va_list ap)
{
    return log_vmsg(LOG_ALERT, format, ap);
}

int
log_vcrit(const char *format, va_list ap)
{
    return log_vmsg(LOG_CRIT, format, ap);
}

int
log_verr(const char *format, va_list ap)
{
    return log_vmsg(LOG_ERR, format, ap);
}

int
log_vwarning(const char *format, va_list ap)
{
    return log_vmsg(LOG_WARNING, format, ap);
}

int
log_vnotice(const char *format, va_list ap)
{
    return log_vmsg(LOG_NOTICE, format, ap);
}

int
log_vinfo(const char *format, va_list ap)
{
    return log_vmsg(LOG_INFO, format, ap);
}

int
log_vdebug(const char *format, va_list ap)
{
    return log_vmsg(LOG_DEBUG, format, ap);
}