# Module:Road data/util

local util = {}  
local insert = table.insert
local concat = table.concat
local format = mw.ustring.format  
---
-- Add all entries in `arr` into `target`.
-- An error is raised if `overwrite` is not true
-- and any key in `arr` is already in `target`.
function util.addAll(target, arr, overwrite)
if type(target) ~= "table" then
error("target is not a table")
end
for key,value in pairs(arr) do
if overwrite or target[key] == nil then
target[key] = value
else
error("Duplicate key: " .. tostring(key))
end
end
end  
local function comp(e1, e2)
local t1 = type(e1)
local t2 = type(e2)
if t1 ~= t2 then return t1 < t2 end
if t1 == "function" then
error("Unexpected function type")
end
return e1 < e2
end  
local arrayToStringAux
arrayToStringAux = function(arr, indent)
if type(arr) ~= "table" then
error("arr is not a table")
end
if type(indent) ~= "number" then
error("indent is not a number")
end
local result = {}
local keys = {}
for key in pairs(arr) do insert(keys, key) end
table.sort(keys, comp)
for _,key in ipairs(keys) do
local value = arr[key]
local keyPrint
if type(key) == "string" then
keyPrint = format("\"%s\"", key)
else
keyPrint = tostring(key)
end
local valuePrint
if type(value) == "table" then
valuePrint = format("{\n%s\n%s}",
arrayToStringAux(value, indent + 4),
string.rep(" ", indent))
elseif type(value) == "string" then
valuePrint = format("\"%s\"", value)
else
valuePrint = tostring(value)
end
insert(result, format("%s[%s] = %s",
string.rep(" ", indent),
keyPrint,
valuePrint))
end
return concat(result, ", \n")
end  
--- Return a string representation of `arr`.
function util.arrayToString(arr, indent)
return arrayToStringAux(arr, indent or 0)
end  
local function convert(distance, multiplier, desiredPrec)
if type(distance) ~= "string" then
error("distance is not a string")
end
if type(multiplier) ~= "number" then
error("multiplier is not a number")
end
-- Import math functions.
local math = require "Module:Math"
-- This function returns the precision of a given string representing a number.
local precision = math._precision
-- This function returns the order of magnitude of a given string representing a number.
local order = math._order
-- This function rounds a given number to the given number of digits.
local round = math._precision_format  
local prec = desiredPrec or precision(distance)
if not desiredPrec then
local ord = order(distance)
-- Adjust precision based on multiplier, as done in .
prec = prec - order(multiplier / 0.2)
end  
local converted = distance * multiplier
local magnitude = order(converted)
if prec <= -magnitude then
-- Ensure the result has at least two significant digits.
prec = -magnitude + 1
end
return round(converted, prec)
end  
---
Convert length specified in one unit (mi or km) to length in the other unit.
@param #map<#string, #string> lengths
a map from unit to distance (as a string) in that unit;
may contain entry `prec` indicating desired conversion precision
@param #string blank text to be used if length is unspecified
@return #table a table containing the conversion result:
orig = source unit;
comp = target unit;
mi = length in miles;
ft = converted length in feet;
km = length in kilometers;
m = converted length in meters;
error = error message, if any  
function util.convertLengths(lengths, blank)
-- Import math functions.
local math = require "Module:Math"
-- In Lua, storing functions locally results in more efficient execution.
-- This function rounds a given number to the given number of digits.
local round = math._precision_format
-- This function returns the precision of a given string representing a number.
local precision = math._precision  
local kmPerMile = 1.609344
local ftPerMile = 5280
-- The length in kilometers as passed to the function.
local km = lengths.km
-- The length in miles as passed to the function.
local mi = lengths.mi
-- Precision for the converted length.
local prec = lengths.prec
local errMsg = {}
-- Sanitize inputs.
local km_ = tonumber(km)
if km and not km_ then
insert(errMsg, util.err("km is not a number"))
end
local mi_ = tonumber(mi)
if mi and not mi_ then
insert(errMsg, util.err("mi is not a number"))
end
local prec_ = tonumber(prec)
if prec and not prec_ then
insert(errMsg, util.err("prec is not a number"))
end
prec = prec_  
local ft
local m
local orig = "mi"
local comp = "km"
if mi and km then
insert(errMsg, util.err("Both mi and km are specified"))
elseif mi then
-- Length in miles was passed.
if mi_ then
-- If `mi` is indeed a number, compute and round the length in kilometers.
km = convert(mi, kmPerMile, prec)
m = convert(mi, kmPerMile * 1000, prec)
-- format mi (insert separators as in 1,000)
mi = round(mi_, precision(mi))
else
-- `mi` is not a number.
km = blank
m = blank
end
elseif km then
-- Length in kilometers was passed.
-- Swap units.
orig, comp = comp, orig
if km_ then
-- If `km` is indeed a number, compute and round the length in miles.
mi = convert(km, 1 / kmPerMile, prec)
ft = convert(km, ftPerMile / kmPerMile, prec)
-- format km (insert separators as in 1,000)
km = round(km_, precision(km))
else
-- `km` is not a number.
mi = blank
ft = blank
end
else
mi = blank
ft = blank
km = blank
m = blank
end
local error = concat(errMsg)
if error == "" then error = nil end
return {mi = mi, ft = ft, km = km, m = m, orig = orig, comp = comp,
error = error}
end  
--- Generates wikitext error messages.
function util.err(msg)
if msg == nil then
error("Unspecified error message")
end
return format('<strong>Error: %s</strong>', msg)
end  
return util