local Units = {}

local Context = nil
local ErrorHandler = nil

--- Initialize Units module with Context dependency
---@param context table The Context module
function Units.initialize(context)
  Context = context
end

--- Initialize ErrorHandler dependency
---@param errorHandler table The ErrorHandler module
function Units.initializeErrorHandler(errorHandler)
  ErrorHandler = errorHandler
end

---@param value string|number
---@return number, string -- Returns numeric value and unit type ("px", "%", "vw", "vh")
function Units.parse(value)
  if type(value) == "number" then
    return value, "px"
  end

  if type(value) ~= "string" then
    if ErrorHandler then
      ErrorHandler.error("Units", string.format("Invalid unit value type. Expected string or number, got %s", type(value)))
    end
    return 0, "px"
  end

  -- Check for invalid format (space between number and unit)
  if value:match("%d%s+%a") then
    if ErrorHandler then
      ErrorHandler.error("Units", string.format("Invalid unit string '%s' (contains space). Use format like '50px' or '50%%'", value))
    end
    return 0, "px"
  end

  -- Match number followed by optional unit
  local numStr, unit = value:match("^([%-]?[%d%.]+)(.*)$")
  if not numStr then
    if ErrorHandler then
      ErrorHandler.error("Units", string.format("Invalid unit format '%s'. Expected format: number + unit (e.g., '50px', '10%%', '2vw')", value))
    end
    return 0, "px"
  end

  local num = tonumber(numStr)
  if not num then
    if ErrorHandler then
      ErrorHandler.error("Units", string.format("Invalid numeric value in '%s'", value))
    end
    return 0, "px"
  end

  -- Default to pixels if no unit specified
  if unit == "" then
    unit = "px"
  end

  local validUnits = { px = true, ["%"] = true, vw = true, vh = true, ew = true, eh = true }
  if not validUnits[unit] then
    if ErrorHandler then
      ErrorHandler.error("Units", string.format("Unknown unit '%s' in '%s'. Valid units: px, %%, vw, vh, ew, eh", unit, value))
    end
    return num, "px"
  end

  return num, unit
end

--- Convert relative units to pixels based on viewport and parent dimensions
---@param value number -- Numeric value to convert
---@param unit string -- Unit type ("px", "%", "vw", "vh", "ew", "eh")
---@param viewportWidth number -- Current viewport width in pixels
---@param viewportHeight number -- Current viewport height in pixels
---@param parentSize number? -- Required for percentage units (parent dimension)
---@return number -- Resolved pixel value
---@throws Error if unit type is unknown or percentage used without parent size
function Units.resolve(value, unit, viewportWidth, viewportHeight, parentSize)
  if unit == "px" then
    return value
  elseif unit == "%" then
    if not parentSize then
      if ErrorHandler then
        ErrorHandler.error("Units", "Percentage units require parent dimension. Element has no parent or parent dimension not available")
      else
        error("Percentage units require parent dimension")
      end
    end
    return (value / 100) * parentSize
  elseif unit == "vw" then
    return (value / 100) * viewportWidth
  elseif unit == "vh" then
    return (value / 100) * viewportHeight
  else
    if ErrorHandler then
      ErrorHandler.error("Units", string.format("Unknown unit '%s'. Valid units: px, %%, vw, vh, ew, eh", unit))
    else
      error(string.format("Unknown unit type: '%s'", unit))
    end
  end
end

---@return number, number -- width, height
function Units.getViewport()
  -- Return cached viewport if available (only during resize operations)
  if Context and Context._cachedViewport and Context._cachedViewport.width > 0 then
    return Context._cachedViewport.width, Context._cachedViewport.height
  end

  if love.graphics and love.graphics.getDimensions then
    return love.graphics.getDimensions()
  else
    local w, h = love.window.getMode()
    return w, h
  end
end

---@param value number
---@param axis "x"|"y"
---@param scaleFactors {x:number, y:number}
---@return number
function Units.applyBaseScale(value, axis, scaleFactors)
  if axis == "x" then
    return value * scaleFactors.x
  else
    return value * scaleFactors.y
  end
end

---@param spacingProps table?
---@param parentWidth number
---@param parentHeight number
---@return table -- Resolved spacing with top, right, bottom, left in pixels
function Units.resolveSpacing(spacingProps, parentWidth, parentHeight)
  if not spacingProps then
    return { top = 0, right = 0, bottom = 0, left = 0 }
  end

  local viewportWidth, viewportHeight = Units.getViewport()
  local result = {}

  local vertical = spacingProps.vertical
  local horizontal = spacingProps.horizontal

  if vertical then
    if type(vertical) == "string" then
      local value, unit = Units.parse(vertical)
      vertical = Units.resolve(value, unit, viewportWidth, viewportHeight, parentHeight)
    end
  end

  if horizontal then
    if type(horizontal) == "string" then
      local value, unit = Units.parse(horizontal)
      horizontal = Units.resolve(value, unit, viewportWidth, viewportHeight, parentWidth)
    end
  end

  for _, side in ipairs({ "top", "right", "bottom", "left" }) do
    local value = spacingProps[side]
    if value then
      if type(value) == "string" then
        local numValue, unit = Units.parse(value)
        local parentSize = (side == "top" or side == "bottom") and parentHeight or parentWidth
        result[side] = Units.resolve(numValue, unit, viewportWidth, viewportHeight, parentSize)
      else
        result[side] = value
      end
    else
      if side == "top" or side == "bottom" then
        result[side] = vertical or 0
      else
        result[side] = horizontal or 0
      end
    end
  end

  return result
end

---@param unitStr string
---@return boolean
function Units.isValid(unitStr)
  if type(unitStr) ~= "string" then
    return false
  end

  local _, unit = Units.parse(unitStr)
  local validUnits = { px = true, ["%"] = true, vw = true, vh = true, ew = true, eh = true }
  return validUnits[unit] == true
end

---@param value string|number -- Value to parse and resolve
---@param viewportWidth number -- Current viewport width
---@param viewportHeight number -- Current viewport height
---@param parentSize number? -- Parent dimension for percentage units
---@return number -- Resolved pixel value
function Units.parseAndResolve(value, viewportWidth, viewportHeight, parentSize)
  local numValue, unit = Units.parse(value)
  return Units.resolve(numValue, unit, viewportWidth, viewportHeight, parentSize)
end

return Units