Module:Chem2

 localgetArgs=require('Module:Arguments').getArgs
 localp={}-- module's table

 -- Elements with wiki links
 localam={
 H="Hydrogen",
 He="Helium",
 Li="Lithium",
 Be="Beryllium",
 B="Boron",
 C="Carbon",
 N="Nitrogen",
 O="Oxygen",
 F="Fluorine",
 Ne="Neon",
 Na="Sodium",
 Mg="Magnesium",
 Al="Aluminium",
 Si="Silicon",
 P="Phosphorus",
 S="Sulfur",
 Cl="Chlorine",
 Ar="Argon",
 K="Potassium",
 Ca="Calcium",
 Sc="Scandium",
 Ti="Titanium",
 V="Vanadium",
 Cr="Chromium",
 Mn="Manganese",
 Fe="Iron",
 Co="Cobalt",
 Ni="Nickel",
 Cu="Copper",
 Zn="Zinc",
 Ga="Gallium",
 Ge="Germanium",
 As="Arsenic",
 Se="Selenium",
 Br="Bromine",
 Kr="Krypton",
 Rb="Rubidium",
 Sr="Strontium",
 Y="Yttrium",
 Zr="Zirconium",
 Nb="Niobium",
 Mo="Molybdenum",
 Tc="Technetium",
 Ru="Ruthenium",
 Rh="Rhodium",
 Pd="Palladium",
 Ag="Silver",
 Cd="Cadmium",
 In="Indium",
 Sn="Tin",
 Sb="Antimony",
 Te="Tellurium",
 I="Iodine",
 Xe="Xenon",
 Cs="Caesium",
 Ba="Barium",
 La="Lanthanum",
 Ce="Cerium",
 Pr="Praseodymium",
 Nd="Neodymium",
 Pm="Promethium",
 Sm="Samarium",
 Eu="Europium",
 Gd="Gadolinium",
 Tb="Terbium",
 Dy="Dysprosium",
 Ho="Holmium",
 Er="Erbium",
 Tm="Thulium",
 Yb="Ytterbium",
 Lu="Lutetium",
 Hf="Hafnium",
 Ta="Tantalum",
 W="Tungsten",
 Re="Rhenium",
 Os="Osmium",
 Ir="Iridium",
 Pt="Platinum",
 Au="Gold",
 Hg="Mercury (element)",
 Tl="Thallium",
 Pb="Lead",
 Bi="Bismuth",
 Po="Polonium",
 At="Astatine",
 Rn="Radon",
 Fr="Francium",
 Ra="Radium",
 Ac="Actinium",
 Th="Thorium",
 Pa="Protactinium",
 U="Uranium",
 Np="Neptunium",
 Pu="Plutonium",
 Am="Americium",
 Cm="Curium",
 Bk="Berkelium",
 Cf="Californium",
 Es="Einsteinium",
 Fm="Fermium",
 Md="Mendelevium",
 No="Nobelium",
 Lr="Lawrencium",
 Rf="Rutherfordium",
 Db="Dubnium",
 Sg="Seaborgium",
 Bh="Bohrium",
 Hs="Hassium",
 Mt="Meitnerium",
 Ds="Darmstadtium",
 Rg="Roentgenium",
 Cn="Copernicium",
 Nh="Nihonium",
 Fl="Flerovium",
 Mc="Moscovium",
 Lv="Livermorium",
 Ts="Tennessine",
 Og="Oganesson",

 -- Groups etc with element-like names
 Bn='Benzyl group',
 Bu='Butyl group',
 Bz='Benzoyl group',
 Cp='Cyclopentadienyl',
 D='Deuterium',
 Et='Ethyl group',
 Ln='Lanthanide',
 Me='Methyl group',
 Nu='Nucleophile',
 Ph='Phenyl group',
 Pn='Pentyl group',
 R='Substituent',
 T='Tritium',
 Tf='Trifluoromethylsulfonyl group',
 X='Halogen',
 }

 -- Groups which are redirected from their normal target if wikilinked; never
 -- autolinked.
 localgroups={
 CH3='Methyl group',
 CO3='Carbonate',
 COOH='Carboxyl group',
 ClO='Hypochlorite',
 ClO2='Chlorite',
 ClO3='Chlorate',
 ClO4='Perchlorate',
 H2O='Water of crystallization',
 H3O='Hydronium',
 NH2='Amine group',
 NH4='Ammonium',
 NO3='Nitrate',
 PO3='Phosphite',
 PO4='Phosphate',
 SH='Thiol group',
 SO3='Sulfite',
 SO4='Sulfate',
 SeH='Selenol group'
 }

 localT_ELEM=0-- token types
 localT_NUM=1-- number
 localT_OPEN=2-- open '('
 localT_CLOSE=3-- close ')'
 localT_PM_CHARGE=4-- + or −
 localT_WATER=6-- .xH2O x number
 localT_CRYSTAL=9-- .x
 localT_CHARGE=8-- charge (x+), (x-)
 localT_SUF_CHARGE=10-- suffix and charge e.g. 2+ from H2+
 localT_SUF_CHARGE2=12-- suffix and (charge) e.g. 2(2+) from He2(2+)
 localT_SPECIAL=14-- starting with \ e.g. \d for double bond (=)
 localT_SPECIAL2=16-- starting with \y{x} e.g. \i{12} for isotope with mass number 12
 localT_ARROW_R=17-- match: ->
 localT_ARROW_EQ=18-- match: <->
 localT_UNDERSCORE=19-- _{ ... }
 localT_CARET=20-- ^{ ... }
 localT_LINKOPEN=21-- Opening of link, always like "[[target|" even if the source wasn't
 localT_NOCHANGE=30-- Anything else like ☃

 functionsu(up,down)
 ifup==""then
 return('<sub class="template-chem2-sub">%s</sub>'):format(down)
 end
 ifdown==""then
 return('<sup class="template-chem2-sup">%s</sup>'):format(up)
 end
 return('<span class="template-chem2-su"><span>%s</span><span>%s</span></span>'):format(up,down)
 end

 functionDotIt()
 return'&middot;'
 end

 functionitem(f)-- (iterator) returns one token (type, value) at a time from the formula 'f'
 locali=1

 returnfunction()
 localt,x=nil,nil

 if(i==1)andf:match('^[0-9]',i)then
 x=f:match('^[%d.]+',i);t=T_NOCHANGE;i=i+x:len();-- matching coefficient (need a space first)

 elseifi<=f:len()then
 x=f:match('^%s+[%d.]+',i);t=T_NOCHANGE;-- matching coefficient (need a space first)
 ifnotxthenx=f:match('^%s[+]',i);t=T_NOCHANGE;end-- matching + (H2O + H2O)
 ifnotxthenx=f:match('^%&%#[%w%d]+%;',i);t=T_NOCHANGE;end-- &#...;
 ifnotxthenx=f:match('^%<%-%>',i);t=T_ARROW_EQ;end-- matching <->
 ifnotxthenx=f:match('^%-%>',i);t=T_ARROW_R;end-- matching ->
 ifnotxthenx=f:match('^%u%l*',i);t=T_ELEM;end-- matching symbols like Aaaaa
 ifnotxthenx=f:match('^%d+[+-]',i);t=T_SUF_CHARGE;end-- matching x+, x-
 ifnotxthenx=f:match('^%d+%(%d*[+-]%)',i);t=T_SUF_CHARGE2;end-- matching x(y+/-), x(+/-)
 ifnotxthenx=f:match('^%(%d*[+-]%)',i);t=T_CHARGE;end-- matching (x+) (xx+), (x-) (xx-)
 ifnotxthenx=f:match('^[%d.]+',i);t=T_NUM;end-- matching number
 ifnotxand(f:match('^%[%[%[[^[]',i)orf:match('^%[[^[]',i))then
 i=i+1;returnT_OPEN,'&#91;'end-- escape [[[X or [X (relevant to auto-linking)
 ifnotxandf:sub(i,i+1)=='[['then
 x=f:match('^%[%[([^]|]*)',i)-- link target
 locallen=x:len()+3
 x='[['..(groups[x]oram[x]orx)..'|'-- override link target for common groups

 iff:sub(len+i,len+i)==']'then
 -- We're going to read the link twice, once as target and once as
 -- chemical markup, e.g. [[CH3]] => "[[CH3|", "CH3]]"
 i=i+2
 else
 i=i+len
 end
 returnT_LINKOPEN,x
 end
 ifnotxthenx=f:match('^[(|{|%[]',i);t=T_OPEN;end-- matching ({[
 ifnotxthenx=f:match('^[)|}|%]]',i);t=T_CLOSE;end-- matching )}]
 ifnotxthenx=f:match('^[+-]',i);t=T_PM_CHARGE;end-- matching + or -
 ifnotxthenx=f:match('^%*[%d.]*H2O',i);t=T_WATER;end-- Crystal water
 ifnotxthenx=f:match('^%*[%d.]*',i);t=T_CRYSTAL;end-- Crystal
 ifnotxthenx=f:match('^[\\].{%d+}',i);t=T_SPECIAL2;end-- \y{x}
 ifnotxthenx=f:match('^[\\].',i);t=T_SPECIAL;end-- \x
 ifnotxthenx=f:match('^_{[^}]*}',i);t=T_UNDERSCORE;end-- _{...}
 ifnotxthenx=f:match('^^{[^}]*}',i);t=T_CARET;end-- ^{...}
 ifnotxthenx=f:match('^.',i);t=T_NOCHANGE;end--the rest - one by one
 ifxtheni=i+x:len();elsei=i+999;error("Invalid character in formula! : "..f)end
 end
 returnt,x
 end
 end

 functionp._chem(args)

 localf=args[1]or''

 f=mw.text.decode(f,true)-- handle entity input (like &minus;): decode right away
 f=string.gsub(f,"–","-")-- replace – with - (hyphen not ndash)
 f=string.gsub(f,"−","-")-- replace – with - (hyphen not minus sign)

 localformula=''
 localt,x

 locallink=args['link']or""
 localauto=args['auto']or""
 localseen={}
 local_debug=false

 ifnot(link=='')thenformula=formula.."[["..link.."|";end-- wikilink start [[link|

 fort,xinitem(f)do
 if_debugthen
 formula=("%s\n* %d %s"):format(formula,t,x)
 elseift==T_ELEMthen
 if(auto=='')or(notam[x])orseen[x]thenformula=formula..x
 elseformula=("%s[[%s|%s]]"):format(formula,am[x],x);seen[x]=true
 end
 elseift==T_COEFFICIENTthenformula=formula..x
 elseift==T_NUMthenformula=formula..su("",x);
 elseift==T_LINKOPENthenformula=formula..x;-- [[Link|
 elseift==T_OPENthenformula=formula..x;-- ([{
 elseift==T_CLOSEthenformula=formula..x;-- )]}
 elseift==T_PM_CHARGEthenformula=formula..su(x:gsub("-","−"),"");
 elseift==T_SUF_CHARGEthen
 formula=formula..su(x:match("[+-]"):gsub("-","−"),x:match("%d+"),"");
 elseift==T_SUF_CHARGE2then
 formula=formula..su(x:match("%(%d*[+-]"):gsub("-","−"):sub(2,-1),x:match("%d+"))
 elseift==T_CHARGEthen
 formula=formula.."<sup>"
 ifx:match("%d+")thenformula=formula..x:match("%d+");end
 formula=formula..x:match("[%+-]"):gsub("-","−").."</sup>";
 -- Cannot concatenat a nil value from x:match("%d+");
 elseift==T_CRYSTALthenformula=formula..DotIt()..string.gsub(x,"*",'',1);
 elseift==T_SPECIALthen
 parameter=x:sub(2,2)-- x fra \x 
 ifparameter=="s"thenformula=formula.."−"-- single bond
 elseifparameter=="d"thenformula=formula.."="-- double bond
 elseifparameter=="t"thenformula=formula.."≡"-- tripple bond
 elseifparameter=="q"thenformula=formula.."≣"-- Quadruple bond
 elseifparameter=="h"thenformula=formula.."η"-- η, hapticity
 elseifparameter=="*"thenformula=formula.."*"-- *, normal *
 elseifparameter=="-"thenformula=formula.."-"-- -
 elseifparameter=="\\"thenformula=formula.."\\"-- \
 elseifparameter=="\'"thenformula=formula.."&#39;"-- html-code for '
 end
 elseift==T_SPECIAL2then-- \y{x}
 parameter=x:sub(2,2)-- y fra \y{x} 
 ifparameter=="h"then--[[Hapticity]]
 if(auto=='')thenformula=formula.."η<sup>"..x:match('%d+').."</sup>-"
 else
 formula=formula.."[[Hapticity|η<sup>"..x:match('%d+').."</sup>]]-"
 end
 elseifparameter=="m"thenformula=formula.."μ<sub>"..x:match('%d+').."</sub>-"-- mu ([[bridging ligand]])
 end
 elseift==T_WATERthen
 ifx:match("^%*[%d.]")then
 formula=formula..DotIt()..x:match("%f[%.%d]%d*%.?%d*%f[^%.%d%]]").."H<sub>2</sub>O";
 else
 formula=formula..DotIt().."H<sub>2</sub>O";
 end
 elseift==T_UNDERSCOREthenformula=formula..su("",x:gsub("-","−"):sub(3,-2))-- x contains _{string}
 elseift==T_CARETthenformula=formula..su(x:gsub("-","−"):sub(3,-2),"")-- x contains ^{string}
 elseift==T_ARROW_Rthenformula=formula.." → "
 elseift==T_ARROW_EQthenformula=formula.." ⇌ "
 elseift==T_NOCHANGEthenformula=formula..x;-- The rest - everything which isn't captured by the regular expresions.
 elseerror('unreachable - ???')end-- in fact, unreachable
 end

 ifnot(link==nilorlink=='')thenformula=formula.."]]";end-- wikilink closing ]]
 formula=mw.getCurrentFrame():preprocess('<templatestyles src="Module:Chem2/styles.css"/>')..
 '<span class="chemf nowrap">'..formula..'</span>'
 ifargs[2]orargs[3]orargs[4]then
 formula=formula..require('Module:If preview')._warning{
 '&#123;&#123;chem2&#125;&#125; was called with multiple positional arguments. It should have just one, e.g. &#123;&#123;chem2&#124;H2O&#125;&#125;.'
 }
 end
 returnformula
 end

 functionp.chem(frame)
 localargs=getArgs(frame)
 returnp._chem(args)
 end

 -- PRIVATE function to generate documentation.
 functionp._autodoc(frame)
 localTableTools=require('Module:TableTools')-- we don't want to load this on articles for no reason
 localresult={
 '===Elements and element-style symbols===\nThese may be automatically linked or used as if they were redirects.\n',
 '{| class="wikitable"\n! Symbol !! Link target\n'
 }
 forsymbol,targetinTableTools.sortedPairs(am)do
 result[#result+1]=('|-\n| %s || [[%s]]\n'):format(symbol,target)
 end
 result[#result+1]='|}\n===Groups===\nThese must be linked manually; they work as if they were redirects.\n'
 result[#result+1]='{| class="wikitable"\n! Symbol !! Link target\n'
 forsymbol,targetinTableTools.sortedPairs(groups)do
 result[#result+1]=('|-\n| %s || [[%s]]\n'):format(symbol,target)
 end
 result[#result+1]='|}'
 returntable.concat(result)
 end

 returnp