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Development tooling for the Mob mobile framework
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lib/mob_dev/qr.ex
defmodule MobDev.QR do
@moduledoc """
Renders QR codes in the terminal using Unicode half-block characters.
Uses eqrcode for matrix generation.
"""
@doc "Prints a QR code for the given content to stdout."
@spec print(String.t()) :: :ok
def print(content) do
IO.puts(render(content))
end
@doc "Returns the QR code as a string of Unicode blocks."
@spec render(String.t()) :: String.t()
def render(content) do
matrix =
content
|> EQRCode.encode()
|> Map.get(:matrix)
|> Tuple.to_list()
|> Enum.map(&Tuple.to_list/1)
# Add a quiet zone (4 cells of whitespace border required by spec)
rows = with_quiet_zone(matrix)
# Process pairs of rows using half-block characters:
# ▀ = top filled, bottom empty
# ▄ = top empty, bottom filled
# █ = both filled
# ' ' = both empty
rows
|> Enum.chunk_every(2, 2, [List.duplicate(0, length(List.first(rows)))])
|> Enum.map_join("\n", fn [top_row, bot_row] ->
Enum.zip(top_row, bot_row)
|> Enum.map_join("", fn
{1, 1} -> "█"
{1, 0} -> "▀"
{0, 1} -> "▄"
{0, 0} -> " "
end)
end)
end
defp with_quiet_zone(matrix) do
width = length(List.first(matrix))
empty_row = List.duplicate(0, width + 8)
side_pad = List.duplicate(0, 4)
padded_rows = Enum.map(matrix, fn row -> side_pad ++ row ++ side_pad end)
List.duplicate(empty_row, 4) ++ padded_rows ++ List.duplicate(empty_row, 4)
end
end