Module:Convert

Documentation for this module may be created at Module:Convert/doc

--[[
TODO Too many items to list, but following are some points:
- Output needs   rather than space in several places.
- Some conversions require two outputs: {{convert|55|nmi|km mi}}.
- Some units have two values: {{convert|3.21|m|ftin}}.
- Remove commas from input numbers; add to output (always?).
- Use U+2212 MINUS SIGN for input + output number, not '-'.
]]--

--[[-----BEGIN DATA TABLE-----
Plan to write a program to generate the conversion tables below.
The input would be a text file in human-friendly format, and
the output would be the following tables.
When a lot of data is added, it might be useful to put this in another module.
Values from http://en.wikipedia.org/wiki/Conversion_of_units
Check with  http://en.wikipedia.org/wiki/Template:Convert/list_of_units
]]--

local units = {
    lookup = function (self, unit)
        -- If unit is known, return its converter table.
        local t = self[unit]
        if t == nil then
            local msg = 'Unit %s not known[[Category:Convert unknown unit]]'
            error(msg:format(unit))
        end
        return t
    end,
    utype = 1,
    scale = 2,
    offset = 3,
    defaultunit = 4,
    ['kg'] =  {'mass',        1,          0,      'lb'},
    ['lb'] =  {'mass',        0.45359237, 0,      'kg'},
    ['m'] =   {'length',      1,          0,      'ft'},
    ['cm'] =  {'length',      0.01,       0,      'in'},
    ['km'] =  {'length',      1000,       0,      'mi'},
    ['mi'] =  {'length',      1609.344,   0,      'km'},
    ['ft'] =  {'length',      0.3048,     0,      'm'},
    ['in'] =  {'length',      0.0254,     0,      'cm'},
    ['K'] =   {'temperature', 1,          273.15, 'C'},
    ['C'] =   {'temperature', 1,          0,      'F'},
    ['F'] =   {'temperature', 5/9,        32,     'C'},
    ['°K'] =  {'temperature', 1,          273.15, '°C'},
    ['°C'] =  {'temperature', 1,          0,      '°F'},
    ['°F'] =  {'temperature', 5/9,        32,     '°C'},
}
-------END DATA TABLE-----

-- Configuration options to keep magic values in one location.
local config = {}

local function get_config(frame)
    -- Return table of configuration options.
    -- Unclear if this is currently needed, but it may help if adapting
    -- code for a different wiki.
    local cfg = {}
    -- Following settings are defaults that can be overridden by template.
    cfg.numdot = '.'        -- decimal mark before fractional digits
    cfg.numsep = ','        -- thousands separator for numbers (',', '.', or nil)
    for k,v in frame:argumentPairs() do
        cfg[k] = v          -- arguments from template's {{#invoke:}}
    end
    -- Following settings are mandatory (to limit abuse).
    cfg.maxsigfig = 20      -- maximum number of significant figures
    return cfg
end

local function withseparator(text)
    -- Return string for a number with thousand separators inserted.
    -- Parameter text is a string like "-12345" or "12345.6789".
    -- Separator is inserted only in the integer part (not in fraction).
    -- Four-digit integer parts have a separator (like "1,234").
    local numsep = config.numsep
    if #numsep == 0 then
        return text
    end
    local function insert(text, first, last)
        local result = ''
        while last >= first do
            if last >= first + 3 then
                result = numsep .. text:sub(last-2, last) .. result
                last = last - 3
            else
                return text:sub(first, last) .. result
            end
        end
        return result
    end
    local first = 1
    local sign = text:sub(first, 1)
    if sign == '+' or sign == '-' then
        -- To handle Unicode minus (multibyte), perhaps use following:
        -- first = text:find('%d')
        first = 2
    else
        sign = ''
    end
    local last = text:find(config.numdot, first, true)
    if last == nil then
        last = #text
    else
        last = last - 1
    end
    return sign .. insert(text, first, last) .. text:sub(last+1)
end

local function formatnumber(value, sigfig)
    -- Return result of converting number 'value' to a string,
    -- rounded to 'sigfig' significant figures.
    local format = string.format
    local rep = string.rep
    local sign = ''
    local numdot = config.numdot
    local function zeropad(text, dot)
        count = sigfig - #text
        if count <= 0 then
            return text
        end
        return text .. dot .. rep('0', count)
    end
    if sigfig <= 0 then
        sigfig = 1
    elseif sigfig > config.maxsigfig then
        sigfig = config.maxsigfig
    end
    if value == 0 then
        return zeropad('0', numdot)
    end
    if value < 0 then
        sign = '-'  -- need proper Unicode minus
        value = -value
    end
    local digits
    local exp, frac = math.modf(math.log10(value))
    if frac == 0 then
        -- Value 1 gives frac = 0, and 0.1 gives frac = -0 (negative zero).
        digits = zeropad('1', '')
        exp = exp + 1  -- adjust so dot is before digits
    else
        local prec = sigfig
        if value > 1 then
            prec = prec - 1  -- will be one sig fig before dot
        end
        digits = format(format('%%.%df', prec), 10^frac)
        if value < 1 then
            -- Is MediaWiki run in a locale where following might be '0,'?
            assert(digits:sub(1, 2) == '0.', 'Bug: rounded number not 0.xxx')
            digits = digits:sub(3)
        else
            if prec == 0 then
                assert(digits:find(numdot, 1, true) == nil, 'Bug: unexpected dot')
            else
                assert(digits:sub(2, 2) == numdot, 'Bug: rounded number not x.xxx')
                digits = digits:sub(1, 1) .. digits:sub(3)
            end
            exp = exp + 1  -- adjust so dot is before digits
        end
    end
    if exp >= #digits then
        digits = digits .. rep('0', exp - #digits)  -- result has no dot
    elseif exp <= 0 then
        digits = '0' .. numdot .. rep('0', -exp) .. digits
    else
        digits = digits:sub(1, exp) .. numdot .. digits:sub(exp+1)
    end
    return sign .. digits
end

local function require_number(value, missing, invalid)
    -- If value is missing or not a number, throw an error.
    -- Thousand separators (valid or not) are first removed.
    -- Return value as a number if valid.
    if value == nil then error(missing) end
    if type(value) == 'number' then return value end
    local numsep = config.numsep
    if #numsep > 0 then value = string.gsub(value, numsep, '') end
    local number = tonumber(value)
    if number == nil then error(invalid:format(value)) end
    return number
end

local function require_integer(value, missing, invalid)
    -- If value is missing or not an integer, throw an error.
    -- Return value as a number if valid.
    local number = require_number(value, missing, invalid)
    if number ~= math.floor(number) then error(invalid:format(value)) end
    return number
end

local function get_parms(pframe)
    -- Return table with all arguments passed by template converted to
    -- named arguments. The numeric args are used to add named args:
    --   in_text, in_text2 (strings given for value, value2)
    --   value, in_unit, out_unit, value2, range, round_to
    -- (except for range, which is nil or a table, the named args that are
    -- added here could be provided by the user of the template).
    local range_types = {  -- text to separate input, output ranges
        ['and'] = {' and ', ' and '},
        ['by'] = {' by ', ' by '},
        ['to'] = {' to ', ' to '},
        ['-'] = {'–', '–'},
        ['to(-)'] = {' to ', '–'},
        ['x'] = {' by ', ' × '},
        ['+/-'] = {' ± ', ' ± '},
    }
    local args = {}                         -- arguments passed to template
    for k,v in pframe:argumentPairs() do
        args[k] = v
    end
    args.in_text = args[1]
    args.value = require_number(args.in_text, 'Need value', 'Value "%s" must be a number')
    local in_unit = args[2]
    local i = 3
    local range = range_types[in_unit]
    if range ~= nil then
        args.in_text2 = args[3]
        args.value2 = require_number(args.in_text2, 'Need second value', 'Second value "%s" must be a number')
        in_unit = args[4]
        i = 5
    end
    local out_unit = args[i]
    local round_to = args[i+1]
    if in_unit == nil then error('Need input unit') end
    args.in_unit = in_unit
    args.out_unit = out_unit
    args.range = range
    args.round_to = args.round_to or round_to  -- allow named parameter
    return args
end

local function default_roundto(intext, factor)
    -- Return a default value for round_to (an integer like 2, 0, -2).
    -- prec = (precision implied in intext)
    --      = (#digits after dot, or negative of #zeroes before dot)
    -- If conversion is multiplication by a factor, and
    -- if factor >= 0.02, compensate prec by adding N where:
    --     N    factor is in range
    --     1     .02  :   .2   =    .1/5 :   .1*2
    --     0     .2   :   2    =    1/5  :   1*2
    --    -1     2    :  20    =   10/5  :  10*2
    --    -2    20    : 200    =  100/5  : 100*2  etc.
    -- TODO Exception required for temperature.
    prec = 0
    dot = intext:find('.', 1, true)
    if dot ~= nil then
        prec = intext:sub(dot+1):len()
        if prec == 0 then
            intext = intext:sub(1, -2)
        end
    end
    if prec == 0 then
        prec = -intext:match('0*$'):len()
    end
    if factor ~= nil and factor >= 0.02 then
        prec = prec - math.floor(math.log10(factor*5))
    end
    return prec
end

local function scaled(value, in_unit, out_unit)
    -- Return scaled value for a simple convert.
    return (value - in_unit[units.offset])
        * (in_unit[units.scale] / out_unit[units.scale])
        + out_unit[units.offset]
end

local function cvtround(invalue, intext, parms)
    -- Convert given invalue using parms (return '' if invalue == nil).
    -- Return rounded, formatted string for result, using rounding
    -- specified in parms.
    -- This code combines convert/round because some rounding requires
    -- knowledge of what we are converting.
    -- TODO Lots of checking required. Will need tweaks for special cases
    -- handled by old Template:Convert.
    -- TODO Limit values to avoid abuse (for example, can currently set
    -- round_to to very large values like 999).
    local text = ''
    if invalue == nil then return text end
    local outvalue = scaled(invalue, parms.in_unit_table, parms.out_unit_table)
    local round_to = parms.round_to
    local sigfig = parms.sigfig
    local disp = parms.disp
    local auto = false
    if round_to then
        -- Ignore sigfig, disp.
        round_to = require_integer(round_to, 'Need value', 'round_to "%s" must be an integer')
    elseif sigfig then
        -- Ignore disp.
        sigfig = require_integer(sigfig, 'Need value', 'sigfig "%s" must be an integer')
        if sigfig <= 0 then
            msg = 'sigfig "%s" must be positive'
            error(msg:format(parms.sigfig))
        end
        text = formatnumber(outvalue, sigfig)
    elseif disp == '5' then
        local negative = false
        if outvalue < 0 then
            negative = true
            outvalue = -outvalue
        end
        outvalue = math.floor((outvalue / 5) + 0.5) * 5
        if negative then
            outvalue = -outvalue
        end
        text = string.format('%.0f', outvalue)
    else
        auto = true  -- using default rounding
        -- TODO If conversion is not multiplication by a number, need factor = nil.
        local factor = outvalue / invalue
        round_to = default_roundto(intext, factor)
    end
    if round_to then
        if round_to >= 0 then
            if auto then
                -- TODO No less than two significant figures.
            end
            local fmt = '%.' .. string.format('%.0f', round_to) .. 'f'
            text = string.format(fmt, outvalue)
        else
            -- This always keeps two sig figs. Should that be done if not auto?
            round_to = -round_to  -- #digits that want to zero
            local maxzeroes = 0  -- maximum #digits that should be zeroed
            if outvalue > 100 then
                maxzeroes = math.log10(outvalue) - 1
            end
            if round_to > maxzeroes then
                round_to = maxzeroes
            end
            if round_to > 0 then
                local scaled = string.format('%.0f', outvalue/(10^round_to))
                text = scaled .. string.rep('0', round_to)
            else
                -- TODO Not satisfactory? Should limit sigfigs?
                text = string.format('%f', outvalue)
            end
        end
    end
    return withseparator(text)
end

local disp_single = {
    ['or'] = '%s %s or %s %s',
    ['sqbr'] = '%s %s [%s %s]',
    ['comma'] = '%s %s, %s %s',
    ['b'] = '%s %s (%s %s)',
}

local disp_double = {
    ['or'] = '%s%s%s %s or %s%s%s %s',
    ['sqbr'] = '%s%s%s %s [%s%s%s %s]',
    ['comma'] = '%s%s%s %s, %s%s%s %s',
    ['b'] = '%s%s%s %s (%s%s%s %s)',
}

local function process(parms)
    -- If we can convert from given in to out unit, return the table values for the two given unit types.
    parms.in_unit_table = units:lookup(parms.in_unit)
    if parms.out_unit == nil then           -- need to catch empty string also?
        parms.out_unit = parms.in_unit_table[units.defaultunit]
    end
    parms.out_unit_table = units:lookup(parms.out_unit)
    if parms.in_unit_table[units.utype] ~= parms.out_unit_table[units.utype] then
        local msg = 'Cannot convert %s to %s'
        error(msg:format(parms.in_unit_table[units.utype], parms.out_unit_table[units.utype]))
    end
    local intext = parms.in_text
    local intext2 = parms.in_text2
    local outext = cvtround(parms.value, intext, parms)
    local outext2 = cvtround(parms.value2, intext2, parms)
    local range = parms.range
    local disp = parms.disp
    local wikitext
    intext = withseparator(intext)  -- TODO what if intext already has commas?
    if range == nil then
        wikitext = disp_single[disp] or disp_single['b']
        wikitext = wikitext:format(intext, parms.in_unit, outext, parms.out_unit)
    else
        wikitext = disp_double[disp] or disp_double['b']
        wikitext = wikitext:format(intext, range[1], intext2, parms.in_unit, outext, range[2], outext2, parms.out_unit)
    end
    return wikitext
end

-- Used by template {{convert2}}.
-- We will have to keep old {{convert}} for a long time, and run
-- {{convert2}} in parallel with {{convert}} while testing/developing.
local p = {}
local bodge = require "Module:mw" -- This fixes up mw.text.tag for us.

function p.convert(frame)
    config = get_config(frame)
    local pframe = frame:getParent()
    local parms = get_parms(pframe)
    local state,text = pcall(process, parms)
    if not state then
        local params = {style="color:black; background-color:orange;"}
        text=mw.text.tag({name="span", contents="[[Module talk:Convert|Conversion error]]: " .. text, params=params})
    end
    return text
end

return p