# Defines some ANSI Terminal Control Escape Sequences.
#
# The color methods (e.g. `Text::green`) format the text to appear colored
# in a ANSI/VT100 terminal. By default, this coloring is skipped if stdout
# is not a TTY, but it can be forced by setting `force_console_colors = true`.
module console

# A ANSI/VT100 escape sequence.
abstract class TermEscape
	# The US-ASCII ESC character.
	protected fun esc: Char do return 27.code_point

	# The Control Sequence Introducer (CSI).
	protected fun csi: String do return "{esc}["
end

# Abstract class of the ANSI/VT100 escape sequences for directional moves.
abstract class TermDirectionalMove
	super TermEscape

	# The length of the move.
	var magnitude: Int = 1 is protected writable

	redef fun to_s do
		if magnitude == 1 then return "{csi}{code}"
		return "{csi}{magnitude}{code}"
	end

	# The code of the command.
	protected fun code: String is abstract
end

# ANSI/VT100 code to move the cursor up by `magnitude` rows (CUU).
class TermMoveUp
	super TermDirectionalMove

	# Move by the specified number of cells.
	init by(magnitude: Int) do self.magnitude = magnitude

	redef fun code do return "A"
end

# ANSI/VT100 code to move the cursor down by `magnitude` rows (CUD).
class TermMoveDown
	super TermDirectionalMove

	# Move by the specified number of cells.
	init by(magnitude: Int) do self.magnitude = magnitude

	redef fun code do return "B"
end

# ANSI/VT100 code to move the cursor forward by `magnitude` columns (CUF).
class TermMoveFoward
	super TermDirectionalMove

	# Move by the specified number of cells.
	init by(magnitude: Int) do self.magnitude = magnitude

	redef fun code do return "C"
end

# ANSI/VT100 code to move the cursor backward by `magnitude` columns (CUB).
class TermMoveBackward
	super TermDirectionalMove

	# Move by the specified number of cells.
	init by(magnitude: Int) do self.magnitude = magnitude

	redef fun code do return "D"
end

# ANSI/VT100 code to move the cursor at the specified position (CUP).
class TermMove
	super TermEscape

	# Vertical position.
	#
	# 1 is the top.
	var row: Int = 1

	# Horizontal position.
	#
	# 1 is the left.
	var column: Int = 1

	# Move at the specified position.
	#
	# (1, 1) is the top-left corner of the display.
	init at(row: Int, column: Int) do
		self.row = row
		self.column = column
	end

	redef fun to_s do
		if row == 1 then
			if column == 1 then return "{csi}H"
			return "{csi};{column}H"
		else
			if column == 1 then return "{csi}{row}H"
			return "{csi}{row};{column}H"
		end
	end
end

# ANSI/VT100 code to clear from the cursor to the end of the screen (ED 0).
class TermEraseDisplayDown
	super TermEscape
	redef fun to_s do return "{csi}J"
end

# ANSI/VT100 code to clear from the cursor to the beginning of the screen (ED 1).
class TermEraseDisplayUp
	super TermEscape
	redef fun to_s do return "{csi}1J"
end

# ANSI/VT100 code to clear the entire display and move the cursor to the top left of screen (ED 2).
#
# Note: Some terminals always move the cursor when the screen is cleared. So we
# force this behaviour to ensure interoperability of the code.
class TermClearDisplay
	super TermEscape
	redef fun to_s do return "{csi}2J{csi}H"
end

# ANSI/VT100 code to erase anything after the cursor in the line (EL 0).
class TermEraseLineFoward
	super TermEscape
	redef fun to_s do return "{csi}K"
end

# ANSI/VT100 code to erase anything before the cursor in the line (EL 1).
class TermEraseLineBackward
	super TermEscape
	redef fun to_s do return "{csi}1K"
end

# ANSI/VT100 code to clear everything in the current line (EL 2).
class TermClearLine
	super TermEscape
	redef fun to_s do return "{csi}2K"
end

# ANSI/VT100 code to save the current cursor position (SCP).
class TermSaveCursor
	super TermEscape
	redef fun to_s do return "{csi}s"
end

# ANSI/VT100 code to restore the current cursor position (RCP).
class TermRestoreCursor
	super TermEscape
	redef fun to_s do return "{csi}u"
end

# ANSI/VT100 code to change character look (SGR).
#
# By default, resets everything to the terminal’s defaults.
#
# Note:
#
# The escape sequence inserted at the end of the string by terminal-related
# methods of `String` resets all character attributes to the terminal’s
# defaults. So, when combining format `a` and `b`, something like
# `("foo".a + " bar").b` will not work as expected, but `"foo".a.b + " bar".b`
# will. You may also use `TermCharFormat` (this class).
#
# Usage example:
#
#     print "{(new TermCharFormat).yellow_fg.bold}a{(new TermCharFormat).yellow_fg}b{new TermCharFormat}"
class TermCharFormat
	super TermEscape

	private var attributes: Array[String] = new Array[String]

	# Copies the attributes from the specified format.
	init from(format: TermCharFormat) do
		attributes.add_all(format.attributes)
	end

	redef fun to_s do return "{csi}{attributes.join(";")}m"

	# Apply the specified SGR and return `self`.
	private fun apply(sgr: String): TermCharFormat do
		attributes.add(sgr)
		return self
	end

	# Apply normal (default) format and return `self`.
	fun default: TermCharFormat do return apply("0")

	# Apply bold weight and return `self`.
	fun bold: TermCharFormat do return apply("1")

	# Apply underlining and return `self`.
	fun underline: TermCharFormat do return apply("4")

	# Apply blinking or bold weight and return `self`.
	fun blink: TermCharFormat do return apply("5")

	# Apply reverse video and return `self`.
	fun inverse: TermCharFormat do return apply("7")

	# Apply normal weight and return `self`.
	fun normal_weight: TermCharFormat do return apply("22")

	# Add the attribute that disable underlining and return `self`.
	fun not_underlined: TermCharFormat do return apply("24")

	# Add the attribute that disable blinking and return `self`.
	fun steady: TermCharFormat do return apply("25")

	# Add the attribute that disable reverse video and return `self`.
	fun positive: TermCharFormat do return apply("27")

	# Apply a black foreground and return `self`.
	fun black_fg: TermCharFormat do return apply("30")

	# Apply a red foreground and return `self`.
	fun red_fg: TermCharFormat do return apply("31")

	# Apply a green foreground and return `self`.
	fun green_fg: TermCharFormat do return apply("32")

	# Apply a yellow foreground and return `self`.
	fun yellow_fg: TermCharFormat do return apply("33")

	# Apply a blue foreground and return `self`.
	fun blue_fg: TermCharFormat do return apply("34")

	# Apply a magenta foreground and return `self`.
	fun magenta_fg: TermCharFormat do return apply("35")

	# Apply a cyan foreground and return `self`.
	fun cyan_fg: TermCharFormat do return apply("36")

	# Apply a white foreground and return `self`.
	fun white_fg: TermCharFormat do return apply("37")

	# Apply the default foreground and return `self`.
	fun default_fg: TermCharFormat do return apply("39")

	# Apply a black background and return `self`.
	fun black_bg: TermCharFormat do return apply("40")

	# Apply a red background and return `self`.
	fun red_bg: TermCharFormat do return apply("41")

	# Apply a green background and return `self`.
	fun green_bg: TermCharFormat do return apply("42")

	# Apply a yellow background and return `self`.
	fun yellow_bg: TermCharFormat do return apply("43")

	# Apply a blue background and return `self`.
	fun blue_bg: TermCharFormat do return apply("44")

	# Apply a magenta background and return `self`.
	fun magenta_bg: TermCharFormat do return apply("45")

	# Apply a cyan background and return `self`.
	fun cyan_bg: TermCharFormat do return apply("46")

	# Apply a white background and return `self`.
	fun white_bg: TermCharFormat do return apply("47")

	# Apply the default background and return `self`.
	fun default_bg: TermCharFormat do return apply("49")
end

# Services to color terminal output
redef class Text
	private fun apply_format(f: TermCharFormat): String do
		if stdout_isatty or force_console_colors then
			return "{f}{self}{normal}"
		else return to_s
	end

	private fun normal: TermCharFormat do return new TermCharFormat

	# Make the text appear in dark gray (or black) in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun gray: String do return apply_format(normal.black_fg)

	# Make the text appear in red in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun red: String do return apply_format(normal.red_fg)

	# Make the text appear in green in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun green: String do return apply_format(normal.green_fg)

	# Make the text appear in yellow in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun yellow: String do return apply_format(normal.yellow_fg)

	# Make the text appear in blue in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun blue: String do return apply_format(normal.blue_fg)

	# Make the text appear in magenta in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun purple: String do return apply_format(normal.magenta_fg)

	# Make the text appear in cyan in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun cyan: String do return apply_format(normal.cyan_fg)

	# Make the text appear in light gray (or white) in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun light_gray: String do return apply_format(normal.white_fg)

	# Make the text appear in bold in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun bold: String do return apply_format(normal.bold)

	# Make the text underlined in a ANSI/VT100 terminal.
	#
	# SEE: `TermCharFormat`
	fun underline: String do return apply_format(normal.underline)
end

# A dynamic progress bar displayable in console.
#
# Example:
# ~~~nitish
# var max = 10
# var current = 0
# var pb = new TermProgress(max, current)
#
# pb.display
# for i in [current + 1 .. max] do
#	nanosleep(1, 0)
#	pb.update(i)
# end
#
# print "\ndone"
# ~~~
#
# Progress bar can accept metadata to display a small amount of data.
#
# Example with metadata:
# ~~~nitish
# var pb = new TermProgress(10, 0)
# for i in [0..10] do
#	pb.update(i, "Step {i}")
# end
# ~~~
class TermProgress

	# Max value of the progress bar (business value).
	var max_value: Int

	# Current value of the progress bar (business value).
	var current_value: Int

	# Number of columns used to display the progress bar.
	var max_columns = 70 is writable

	# Get the current percent value.
	fun current_percentage: Int do
		return current_value * 100 / max_value
	end

	# Display the progress bar.
	#
	# `metadata`  can be used to pass a small amount of data to display after
	# the progress bar.
	fun display(metadata: nullable String) do
		var percent = current_percentage
		var p = current_value * max_columns / max_value
		printn "\r{percent}% ["
		for i in [1..max_columns] do
			if i < p then
				printn "="
			else if i == p then
				printn ">"
			else
				printn " "
			end
		end
		printn "]"
		if metadata != null then printn " ({metadata})"
	end

	# Update and display the progress bar.
	#
	# See `display`.
	fun update(new_current: Int, metadata: nullable String) do
		current_value = new_current
		display(metadata)
	end
end

redef class Sys
	private var stdout_isatty: Bool = 1.isatty is lazy

	# Force coloring terminal output, even if stdout is not a TTY?
	#
	# Defaults to `false`.
	var force_console_colors = false is writable
end