local util = {}

local function byte(value, offset)
  return bit.band(bit.rshift(value, offset), 0xFF)
end

local function rgb(color)
  color = vim.api.nvim_get_color_by_name(color)

  if color == -1 then
    color = vim.opt.background:get() == "dark" and 000 or 255255255
  end

  return {byte(color, 16), byte(color, 8), byte(color, 0)}
end

local function parse_color(color)
  if color == nil then return print("invalid color") end

  color = color:lower()

  if not color:find("#") and color ~= "none" then
    color = require("rose-pine.palette")[color] or
                vim.api.nvim_get_color_by_name(color)
  end

  return color
end

---@param fg string foreground color
---@param bg string background color
---@param alpha number number between 0 (background) and 1 (foreground)
util.blend = function(fg, bg, alpha)
  fg = rgb(parse_color(fg))
  bg = rgb(parse_color(bg))

  local function blend_channel(i)
    local ret = (alpha * fg[i] + ((1 - alpha) * bg[i]))
    return math.floor(math.min(math.max(0, ret), 255) + 0.5)
  end

  return string.format("#%02X%02X%02X", blend_channel(1), blend_channel(2),
                       blend_channel(3))
end

---@param group string
---@param color table<string, string>
util.highlight = function(group, color)
  local style = color.style and "gui=" .. color.style or "gui=NONE"
  local fg = color.fg and "guifg=" .. parse_color(color.fg) or "guifg=NONE"
  local bg = color.bg and "guibg=" .. parse_color(color.bg) or "guibg=NONE"
  local sp = color.sp and "guisp=" .. parse_color(color.sp) or ""

  vim.cmd(string.format("highlight %s %s %s %s %s", group, style, fg, bg, sp))

  if color.link then
    vim.cmd(string.format("highlight! link %s %s", group, color.link))
  end
end

return util