/** @file console.c
 *
 *  @brief Console driver implementation.
 *
 *  @author Hanjie Wu (hanjiew)
 *  @bug No functional bugs
 */

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <string.h>

#include <x86/asm.h>
#include <x86/video_defines.h>

#include <interrupt.h>
#include <paging.h>
#include <pts.h>
#include <pv.h>
#include <sched.h>
#include <sync.h>
#include <usermem.h>

/** index of the register to start displaying cursor */
#define CRTC_CURSOR_START 10
/** bit to start displaying cursor */
#define CURSOR_ENABLE_BIT 0x20

/** pointer to the viedo memory at B800h */
a_char_on_screen_t (*console_mem)[CONSOLE_WIDTH] =
    (a_char_on_screen_t(*)[CONSOLE_WIDTH])CONSOLE_MEM_BASE;

/** the char used to produce blank */
#define BLANK_CH ' '
/** initial color of the cursor */
#define DEFAULT_COLOR (FGND_WHITE | BGND_BLACK)

pts_t* active_pts = NULL;
spl_t pts_lock = SPL_INIT;
/** all pts structures */
queue_t* all_pts = NULL;

pts_t kernel_pts;

void setup_pts() {
    pts_init(&kernel_pts);
    kernel_pts.refcount++; /* kernel's refcount for all kths */
    active_pts = &kernel_pts;
}

void pts_init(pts_t* pts) {
    pts->cur_x = pts->cur_y = 0;
    pts->cur_color = DEFAULT_COLOR;
    pts->cur_shown = 1;

    pts->reqs = NULL;
    pts->kbd_request_lock = MUTEX_INIT;
    pts->kbd_request_cv = CV_INIT;
    pts->input_lock = MUTEX_INIT;
    pts->input_cv = CV_INIT;
    pts->kh_r_pos = pts->kh_w_pos = 0;
    pts->chr_r_pos = pts->chr_w_pos = 0;
    pts->forward_tab = 0;

    pts->lock = MUTEX_INIT;
    pts->pvs = NULL;
    pts->refcount = 0;
    queue_insert_tail(&all_pts, &pts->pts_link);
}

void switch_pts(pts_t* new_pts) {
    int old_if = spl_lock(&pts_lock);
    pts_t* pts = active_pts;
    active_pts = new_pts;
    if (pts->refcount == 0) {
        queue_detach(&all_pts, &pts->pts_link);
        sfree(pts, sizeof(pts_t));
    }
    memcpy(console_mem, new_pts->mem, sizeof(new_pts->mem));
    int pos = new_pts->cur_y * CONSOLE_WIDTH + new_pts->cur_x;
    outb(CRTC_IDX_REG, CRTC_CURSOR_LSB_IDX);
    outb(CRTC_DATA_REG, pos & 0xff);
    outb(CRTC_IDX_REG, CRTC_CURSOR_MSB_IDX);
    outb(CRTC_DATA_REG, pos >> 8);
    spl_unlock(&pts_lock, old_if);
}

/**
 * @brief Move the cursor to a position. Position is checked before calling this
 * function
 * @param pts pts
 * @param x x
 * @param y y
 */
static inline void move_cursor(pts_t* pts, int x, int y) {
    pts->cur_x = x;
    pts->cur_y = y;
    int old_if = spl_lock(&pts_lock);
    if (active_pts == pts) {
        int pos = y * CONSOLE_WIDTH + x;
        outb(CRTC_IDX_REG, CRTC_CURSOR_LSB_IDX);
        outb(CRTC_DATA_REG, pos & 0xff);
        outb(CRTC_IDX_REG, CRTC_CURSOR_MSB_IDX);
        outb(CRTC_DATA_REG, pos >> 8);
    }
    spl_unlock(&pts_lock, old_if);
}

/**
 * @brief Scroll the console by one line and clean the last line
 */
static inline void scroll_page(pts_t* pts) {
    /* move all but last line forward */
    memmove(pts->mem[0], pts->mem[1],
            sizeof(a_char_on_screen_t) * CONSOLE_WIDTH * (CONSOLE_HEIGHT - 1));
    int i;
    for (i = 0; i < CONSOLE_WIDTH; i++) {
        pts->mem[CONSOLE_HEIGHT - 1][i] =
            (a_char_on_screen_t){BLANK_CH, pts->cur_color};
    }
    int old_if = spl_lock(&pts_lock);
    if (active_pts == pts) {
        memmove(
            console_mem[0], console_mem[1],
            sizeof(a_char_on_screen_t) * CONSOLE_WIDTH * (CONSOLE_HEIGHT - 1));
        int i;
        for (i = 0; i < CONSOLE_WIDTH; i++) {
            console_mem[CONSOLE_HEIGHT - 1][i] =
                (a_char_on_screen_t){BLANK_CH, pts->cur_color};
        }
    }
    spl_unlock(&pts_lock, old_if);
}

static inline void draw_char(pts_t* pts,
                             int row,
                             int col,
                             a_char_on_screen_t ch) {
    pts->mem[row][col] = ch;
    int old_if = spl_lock(&pts_lock);
    if (active_pts == pts) {
        console_mem[row][col] = ch;
    }
    spl_unlock(&pts_lock, old_if);
}

int putbyte(char ch) {
    if (active_pts == NULL) {
        /* this only happens when panicking before setup_pts */
        active_pts = &kernel_pts;
        pts_putbyte(&kernel_pts, ch);
        active_pts = NULL;
        return 0;
    }
    return pts_putbyte(get_current()->pts, ch);
}

int pts_putbyte(pts_t* pts, char ch) {
    if (ch == '\n') {
        if (pts->cur_y < CONSOLE_HEIGHT - 1) {
            move_cursor(pts, 0, pts->cur_y + 1);
        } else {
            scroll_page(pts);
            move_cursor(pts, 0, pts->cur_y);
        }
        return ch;
    }
    if (ch == '\r') {
        move_cursor(pts, 0, pts->cur_y);
        return ch;
    }
    if (ch == '\b') {
        if (pts->cur_x > 0) {
            move_cursor(pts, pts->cur_x - 1, pts->cur_y);

        } else if (pts->cur_y > 0) {
            move_cursor(pts, CONSOLE_WIDTH - 1, pts->cur_y - 1);
        }
        a_char_on_screen_t c = {BLANK_CH, pts->cur_color};
        draw_char(pts, pts->cur_y, pts->cur_x, c);
        return ch;
    }
    /* save the position where we should show the char */
    int prev_x = pts->cur_x, prev_y = pts->cur_y;
    if (pts->cur_x < CONSOLE_WIDTH - 1) {
        /* move forward */
        move_cursor(pts, pts->cur_x + 1, pts->cur_y);
    } else if (pts->cur_y < CONSOLE_HEIGHT - 1) {
        /* go to next line */
        move_cursor(pts, 0, pts->cur_y + 1);
    } else {
        /* scroll and go to beginning of the line */
        scroll_page(pts);
        move_cursor(pts, 0, pts->cur_y);
        prev_y -= 1;
    }
    a_char_on_screen_t c = {ch, pts->cur_color};
    draw_char(pts, prev_y, prev_x, c);
    return ch;
}

void pts_putbytes(pts_t* pts, const char* s, int len) {
    if (s == NULL || len <= 0) {
        return;
    }
    int i;
    for (i = 0; i < len; i++) {
        pts_putbyte(pts, s[i]);
    }
}

int pts_set_term_color(pts_t* pts, int color) {
    if (color > 0xff || color < 0) {
        return -1;
    }
    pts->cur_color = (char)color;
    return 0;
}

void pts_get_term_color(pts_t* pts, int* color) {
    *color = pts->cur_color;
}

int pts_set_cursor(pts_t* pts, int row, int col) {
    if (row >= CONSOLE_HEIGHT || row < 0) {
        return -1;
    }
    if (col >= CONSOLE_WIDTH || col < 0) {
        return -1;
    }
    move_cursor(pts, col, row);
    return 0;
}

void pts_get_cursor(pts_t* pts, int* row, int* col) {
    *row = pts->cur_y;
    *col = pts->cur_x;
}

int pts_print_at(pts_t* pts, int len, va_t buf, int row, int col, int color) {
    int old_row, old_col;
    int old_color;
    pts_get_cursor(pts, &old_row, &old_col);
    if (pts_set_cursor(pts, row, col) != 0) {
        goto bad_pos;
    }
    pts_get_term_color(pts, &old_color);
    if (pts_set_term_color(pts, color) != 0) {
        goto bad_color;
    }
    if (print_buf_from_user(pts, buf, len) != 0) {
        goto bad_print;
    }
    pts_set_term_color(pts, old_color);
    pts_set_cursor(pts, old_row, old_col);
    return 0;

bad_print:
    pts_set_term_color(pts, old_color);
bad_color:
    pts_set_cursor(pts, old_row, old_col);
bad_pos:
    return -1;
}

/**
 * @brief keyboard inturrupt handler
 */
void kbd_handler_real(stack_frame_t* f) {
    unsigned char sc = inb(KEYBOARD_PORT);
    pic_acknowledge(KBD_IRQ);
    pts_t* pts = active_pts;
    int should_insert = 0;
    kh_type kh = process_scancode(sc);
    if (KH_HASDATA(kh) && KH_ISMAKE(kh)) {
        should_insert = 1;
        if (KH_GETCHAR(kh) == KHE_TAB) {
            if (KH_SHIFT(kh) != 0) {
                if (pts->forward_tab == 0) {
                    pts->forward_tab = 1;
                    return;
                }
                /* else forward shift+tab to client */
            } else if (KH_CTL(kh) != 0) {
                if (pts->forward_tab != 0) {
                    pts->forward_tab = 0;
                    return;
                }
            } else if (pts->forward_tab == 0) {
                pts_t* new_pts =
                    queue_data(pts->pts_link.next, pts_t, pts_link);
                if (new_pts != pts) {
                    switch_pts(new_pts);
                }
                return;
            }
        }
    }
    if (pts->pvs != NULL) {
        pv_t* pv = queue_data(pts->pvs, pv_t, pts_link);
        pv_pend_irq(pv, KEY_IDT_ENTRY, kh);
        return;
    }
    if (should_insert != 0) {
        int next_w_pos = (pts->kh_w_pos + 1) % KH_RING_SIZE;
        if (next_w_pos != pts->kh_r_pos) {
            pts->kh_ring[pts->kh_w_pos] = kh;
            pts->kh_w_pos = next_w_pos;
        }
    }
    cv_signal(&pts->input_cv);
}

/**
 * @brief process scancode until a char is produced
 * @return char produced
 */
static int sc_process(pts_t* pts);

/**
 * @brief flush a line to user buffer
 * @param len length of buffer
 * @param buf buffer
 * @return size of chars flushed, -1: buf invalid
 */
static int flush_line(pts_t* pts, int len, va_t buf);

int do_readline(int len, va_t buf) {
    if (len < 0 || len > MAX_READLINE) {
        return -1;
    }
    if (len == 0) {
        return 0;
    }
    pts_t* pts = get_current()->pts;
    kbd_request_t req;
    req.t = get_current();
    /* wait until our turn */
    mutex_lock(&pts->kbd_request_lock);
    queue_insert_tail(&pts->reqs, &req.node);
    while (pts->reqs != &req.node) {
        cv_wait(&pts->kbd_request_cv, &pts->kbd_request_lock);
    }
    mutex_unlock(&pts->kbd_request_lock);
    int should_flush = 0;
    if (pts->chr_r_pos != pts->chr_w_pos) {
        int i;
        for (i = pts->chr_r_pos; i != pts->chr_w_pos;
             i = (i + 1) % CHR_RING_SIZE) {
            if (pts->chr_ring[i] == '\n') {
                should_flush = 1;
                break;
            }
        }
        /* check if ring is full */
        if (pts->chr_r_pos == (pts->chr_w_pos + 1) % CHR_RING_SIZE) {
            should_flush = 1;
        }
    }
    while (should_flush == 0) {
        /* wait for more chars */
        char c = sc_process(pts);
        if (c == '\b') {
            if (pts->chr_w_pos != pts->chr_r_pos) {
                pts_putbyte(pts, c);
                pts->chr_w_pos =
                    (pts->chr_w_pos + CHR_RING_SIZE - 1) % CHR_RING_SIZE;
            }
        } else {
            pts->chr_ring[pts->chr_w_pos] = c;
            pts->chr_w_pos = (pts->chr_w_pos + 1) % CHR_RING_SIZE;
            pts_putbyte(pts, c);
            should_flush =
                (c == '\n') ||
                (pts->chr_r_pos == (pts->chr_w_pos + 1) % CHR_RING_SIZE);
        }
    }
    int result = flush_line(pts, len, buf);
    mutex_lock(&pts->kbd_request_lock);
    queue_detach(&pts->reqs, &req.node);
    cv_signal(&pts->kbd_request_cv);
    mutex_unlock(&pts->kbd_request_lock);
    return result;
}

int do_getchar() {
    pts_t* pts = get_current()->pts;
    kbd_request_t req;
    req.t = get_current();
    mutex_lock(&pts->kbd_request_lock);
    queue_insert_tail(&pts->reqs, &req.node);
    while (pts->reqs != &req.node) {
        cv_wait(&pts->kbd_request_cv, &pts->kbd_request_lock);
    }
    mutex_unlock(&pts->kbd_request_lock);
    int result;
    if (pts->chr_r_pos != pts->chr_w_pos) {
        result = pts->chr_ring[pts->chr_r_pos];
        pts->chr_r_pos = (pts->chr_r_pos + 1) % CHR_RING_SIZE;
    } else {
        result = sc_process(pts);
    }
    mutex_lock(&pts->kbd_request_lock);
    queue_detach(&pts->reqs, &req.node);
    cv_signal(&pts->kbd_request_cv);
    mutex_unlock(&pts->kbd_request_lock);
    return result;
}

static int flush_line(pts_t* pts, int len, va_t buf) {
    int size = 0, i;
    for (i = pts->chr_r_pos; i != pts->chr_w_pos; i = (i + 1) % CHR_RING_SIZE) {
        size++;
        if (pts->chr_ring[i] == '\n') {
            break;
        }
    }
    if (size > len) {
        size = len;
    }
    int end_pos = (pts->chr_r_pos + size) % CHR_RING_SIZE;
    if (end_pos > pts->chr_r_pos) {
        if (copy_to_user(buf, size, &pts->chr_ring[pts->chr_r_pos]) != 0) {
            return -1;
        }
    } else {
        int size_1 = (CHR_RING_SIZE - pts->chr_r_pos);
        if (copy_to_user(buf, size_1, &pts->chr_ring[pts->chr_r_pos]) != 0) {
            return -1;
        }
        if (copy_to_user(buf + size_1, end_pos, &pts->chr_ring[0]) != 0) {
            return -1;
        }
    }
    pts->chr_r_pos = end_pos;
    return size;
}

static int sc_process(pts_t* pts) {
    while (1) {
        /* wait for more scancode */
        mutex_lock(&pts->input_lock);
        while (pts->kh_r_pos == pts->kh_w_pos) {
            cv_wait(&pts->input_cv, &pts->input_lock);
        }
        kh_type kh = pts->kh_ring[pts->kh_r_pos];
        pts->kh_r_pos = (pts->kh_r_pos + 1) % KH_RING_SIZE;
        mutex_unlock(&pts->input_lock);
        return KH_GETCHAR(kh);
    }
}