// VD.js -- a viewdata terminal emulator

// constructor
function VD(wd, ht, scr_id, initscr)
{
	var r;
	var c;
	var scr = document.getElementById(scr_id);

	this.wd_ = wd;
	this.ht_ = ht;
	this.text_ = new Array(ht);
	for (r=0; r<ht; ++r) {
		this.text_[r] = new Array(wd);
	}

	this.scr_ = scr;
	this.cursor_vis_ = true;
	this.reveal_ = 0;
        this.getch_isr_ = undefined;
	this.grab_events_ = false;
	this.key_buf_ = [];
	this.esc_state_ = 0;
	this.col_ = 0;
	this.row_ = 0;

	// Initial Screen
	if (typeof initscr !== 'undefined') {
		this.write("\x0c" + this.txthash(initscr) + "\x14\x1e");
	} else {
		this.write("\x0c\x11\x1e");
	}
}

VD.A_REVERSE = 2;
VD.A_BLINK = 4;

// class variables
VD.the_vt_ = undefined;

// object methods
VD.prototype.html_colours_ = function(at_fg, at_bg, at_mode) {
	var co0, co1;
	if (at_mode & VD.A_REVERSE) {
		co0 = 'ff';
		co1 = '00';
	} else {
		co0 = '00';
		co1 = 'ff';
	}

	return {
		f: '#' + (at_fg & 1 ? co1 : co0) +
			 (at_fg & 2 ? co1 : co0) +
			 (at_fg & 4 ? co1 : co0),
		b: '#' + (at_bg & 1 ? co1 : co0) +
			 (at_bg & 2 ? co1 : co0) +
			 (at_bg & 4 ? co1 : co0)
	    };
}

VD.prototype.txthash = function(hashstring) {
	var currentcode = 0, stuff = '';

	if (hashstring.indexOf(':') > -1)
		var hashstring = hashstring.split(':')[1];

	hashstring = hashstring.substring(0,this.wd_*this.ht_);

	for (var p=0; p<hashstring.length; p++) {
		var pc = hashstring.charAt(p);
		var pc_dec = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"
			.indexOf(hashstring.charAt(p));

		// b is the bit in the 6-bit base-64 character.
		for (var b=0; b<6; b++) {
			// The current bit position in the character being
			// written to.
			var charbit = (6*p+b) % 7;

			// The bit value (set or unset) of the bit we're
			// reading from.
			var b64bit = pc_dec & (1 << (5-b));
			if ( b64bit > 0 ) {
				b64bit = 1;
			}

			// Update the current code.
			currentcode |= b64bit << (6-charbit);

			// If we've reached the end of this character cell
			// and it's the last bit in the character we're
			// writing to, set the character code or place the
			// code.
			if (charbit === 6) {
				if (currentcode < 32) {
					stuff += '\x1b';
					currentcode += 64;
				}

				stuff += String.fromCharCode(currentcode);
				currentcode = 0;
			}
		}
	}

	return stuff;
}

VD.prototype.clear = function() {
	this.row_ = this.col_ = 0;

	for (r=0; r<this.ht_; ++r) {
		for (c = 0; c < this.wd_; ++c) {
			this.text_[r][c] = ' ';
		}
	}
}

VD.prototype.curs_set = function(vis) {
	if (vis !== undefined)
		this.cursor_vis_ = (vis > 0);
}

VD.prototype.getch = function(isr) {
        this.getch_isr_ = isr;

        setTimeout(VD.go_getch_, 0);
}

VD.go_getch_ = function VD_go_getch() {
        var vt = VD.the_vt_;
        if (vt === undefined)
                return;

        var isr = vt.getch_isr_;
        vt.getch_isr_ = undefined;
        if (isr === undefined)
                return;

        var ch = vt.key_buf_.shift();
        if (ch === undefined) {
                vt.getch_isr_ = isr;
                return;
        }

        isr(ch,vt);
}

VD.prototype.move = function(r, c) {
	if (r < 0)
		r = 0;

	else if (r >= this.ht_)
		r = this.ht_ - 1;

	if (c < 0)
		c = 0;

	else if (c >= this.wd_)
		c = this.wd_ - 1;
	this.row_ = r;
	this.col_ = c;
}

VD.prototype.refresh = function() {
	var r, c, stuff = "", start_tag = "", end_tag = "", ch, chtype,
	    pair, cr, cc, ht, wd, cv, n_fg, n_bg, n_mode, n_type, a_fg=-1, a_bg=-1, a_mode=-1, n_dblnextline=-2, n_heldchar, n_heldtype;
	ht = this.ht_;
	wd = this.wd_;
	cr = this.row_;
	cc = this.col_;
	cv = this.cursor_vis_;

	if (cc >= wd)
		cc = wd - 1;

	for (r = 0; r < ht; ++r) {
		if (r > 0) {
			stuff += '\n';
		}

		n_fg = 7;
		n_bg = 0;
		n_mode = 0;
		n_type = 0;
		n_heldchar = 32;
		n_heldtype = 0;

		if (n_dblnextline+1 < r)
			n_dblnextline = -2;

		for (c = 0; c < wd; ++c) {
			if (cv && r == cr && c == cc) {
				// Draw the cursor here.
				n_mode |= VD.A_REVERSE;
			} else {
				n_mode &= ~VD.A_REVERSE;
			}

			if (r == n_dblnextline+1) {
				ch = this.text_[r-1][c].charCodeAt(0);
			} else {
				ch = this.text_[r][c].charCodeAt(0);
			}

			ctrlch = ch;

// set-at
			if (ctrlch == 0x89) // steady
				n_mode &= ~VD.A_BLINK;

			if (ctrlch == 0x8c) { // normal
				if (n_type & 8) {
					n_heldchar = 32;
					n_heldtype = 0;
				}
				n_type &= ~8;
			}

			if (ctrlch == 0x98 && this.reveal_ == false) // conceal
				n_type |= 16;

			if (ctrlch == 0x99) // contig
				n_type &= ~1;

			if (ctrlch == 0x9a) // sep
				n_type |= 1;

			if (ctrlch == 0x9c) // black
				n_bg = 0;

			if (ctrlch == 0x9d) // newback
				n_bg = n_fg;

			if (ctrlch == 0x9e) // hold
				n_type |= 32;

			// If the attributes changed, make a new span.
			if (n_mode != a_mode || n_fg != a_fg || n_bg != a_bg) {
				stuff += end_tag;
				pair = this.html_colours_(n_fg, n_bg, n_mode);
				stuff += '<span style="color:' + pair.f + ';background-color:' + pair.b + ";" +'">'
				end_tag = "</span>";
				if (n_mode & VD.A_BLINK) {
					stuff += '<span class="flashing";>';
					end_tag += "</span>";
				}
				a_fg = n_fg;
				a_bg = n_bg;
				a_mode = n_mode;
			}

			chtype = n_type;

			if (ch >= 128) {
				if (n_type & 32) {
					ch = n_heldchar;
					chtype = n_heldtype;
				} else {
					ch = 32;
				}
			}

			if (ch == 127) {
				if (n_type & 2) {
					ch = 0xe23f+((chtype & 1)*0xc0);
					n_heldchar = 127;
				} else {
					ch = 0xb6;
				}
			}

			if (n_type & 2) {
				if ( ch >= 0x20 && ch <= 0x3f) {
					n_heldchar = ch;
					ch = ch+0xe1e0+((chtype & 1)*0xc0);
				} else if ( ch >= 0x60 && ch <= 0x7e) {
					n_heldchar = ch;
					ch = ch+0xe1c0+((chtype & 1)*0xc0);
				}
			}

			if (n_type & 16)
				ch = 32;

			n_heldtype = chtype;

			switch (ch) {
			    case 32:
				ch = 0xa0; break;
			    case 0x7e:
			    	ch = 0xf7; break;
			    case 0x5f: // _
			    	ch = 0x23; break // #
			    case 123: // {
			    	ch = 0xbc; break
			    case 92: // \
			    	ch = 0xbd; break
			    case 125: // }
			    	ch = 0xbe; break
			    case 0x23: // #
			    	ch = 0xa3; break
			}

			if (n_type & 8) {
				if (ch < 0x100) {
					ch = ch+0xe000+((r==n_dblnextline+1)*0x100);
				} else {
					ch = ch+0x40+((r==n_dblnextline+1)*0x40)
				}

			} else if (r==n_dblnextline+1) {
				ch = 0xa0;
			}

			stuff += "&#x" + ch.toString(16) + ";"

// set-after
			if (ctrlch >= 129 && ctrlch <= 135) {
				if (n_type & 2) {
					n_heldchar=32;
					n_heldtype=0;
				}
				n_fg = ctrlch-128;
				n_type &= ~2;
				n_type &= ~16;
			}

			if (ctrlch >= 145 && ctrlch <= 151) {
				if (n_type & 2 == 0) {
					n_heldchar=32;
					n_heldtype=0;
				}
				n_fg = ctrlch-144;
				n_type |= 2;
				n_type &= ~16;
			}

			if (ctrlch == 0x88) // flash
				n_mode |= VD.A_BLINK;

			if (ctrlch == 0x8d) { // double
				if (n_type & 8 == 0) {
					n_heldchar = 32;
					n_heldtype = 0;
				}
				n_type |= 8;
				if (n_dblnextline < 0)
					n_dblnextline = r;
			}

			if (ctrlch == 0x9f) // release
				n_type &= ~32;
		}
	}

	stuff += end_tag
	this.scr_.innerHTML = "<b>" + stuff + "</b>\n";
}

VD.prototype.write = function(stuff) {
	var ch, i;

	for (i = 0; i < stuff.length; ++i) {
		ch = stuff.charCodeAt(i);

		if (this.esc_state_ && ch > 31)
			ch = (ch % 32) + 128;

		this.esc_state_ = 0;

		switch (ch) {
			case 8:
				if (this.col_ != 0) {
					--this.col_;
				} else {
					this.col_ = this.wd_-1;
					if (this.row_ == 0) {
						this.row_ = this.ht_-1;
					} else {
						--this.row_;
					}
				}

				break;

			case 9:
				if (this.col_ >= this.wd_) {
					this.col_ = 0;
					if (this.row_ == this.ht_-1) {
				    		this.row_ = 0;
					} else {
						++this.row_;
					}
				} else {
					++this.col_;
				}

				break;

			case 10:
				if (this.row_ >= this.ht_-1) {
		    			this.row_ = 0;
				} else {
					++this.row_;
				}

				break;

			case 11:
				if (this.row_ == 0) {
		    			this.row_ = this.ht_-1;
				} else {
					--this.row_;
				}

				break;

			case 12:
				this.clear();
				this.move(0, 0);
				this.reveal_ = false;

				break;

			case 13:
				this.col_ = 0;
				break;
			case 17:
				this.curs_set(1);
				break;
			case 20:
				this.curs_set(0);
				break;
			case 27:
				this.esc_state_ = 1;
				break;
			case 30:
				this.move(0, 0);
				break;
			default:
				if (ch > 31) {
					this.text_[this.row_][this.col_] = String.fromCharCode(ch);

					if (this.col_ >= this.wd_-1) {
						this.col_ = 0;

						if (this.row_ >= this.ht_-1) {
					    		this.row_ = 0;
						} else {
							++this.row_;
						}

					} else {
						++this.col_;
					}
				}
		}
	}

	this.refresh();
}