spacevim/bundle/vim-mail/syntax/mail.vim

"=============================================================================
" mail.vim --- mail syntax file for vim
" Copyright (c) 2016-2022 Shidong Wang & Contributors
" Author: Shidong Wang < wsdjeg@outlook.com >
" URL: https://github.com/vim-mail/vim-mail
" License: MIT license
"=============================================================================

" Quit when a syntax file was already loaded
if exists("b:current_syntax")
  finish
endif

" The mail header is recognized starting with a "keyword:" line and ending
" with an empty line or other line that can't be in the header. All lines of
" the header are highlighted. Headers of quoted messages (quoted with >) are
" also highlighted.

" Syntax clusters
syn cluster mailHeaderFields	contains=mailHeaderKey,mailSubject,mailHeaderEmail,@mailLinks
syn cluster mailLinks		contains=mailURL,mailEmail
syn cluster mailQuoteExps	contains=mailQuoteExp1,mailQuoteExp2,mailQuoteExp3,mailQuoteExp4,mailQuoteExp5,mailQuoteExp6

syn case match
" For "From " matching case is required. The "From " is not matched in quoted
" emails
syn region	mailHeader	contains=@mailHeaderFields start="^From " skip="^\s" end="\v^[-A-Za-z0-9]*([^-A-Za-z0-9:]|$)"me=s-1
syn match	mailHeaderKey	contained contains=mailEmail "^From\s.*$"

syn case ignore
" Nothing else depends on case. Headers in properly quoted (with "> " or ">")
" emails are matched
syn region	mailHeader	contains=@mailHeaderFields,@mailQuoteExps start="^\z(\(> \?\)*\)\v(newsgroups|from|((in-)?reply-)?to|b?cc|subject|return-path|received|date|replied):" skip="^\z1\s" end="\v^\z1[-a-z0-9]*([^-a-z0-9:]|$)"me=s-1 end="\v^\z1@!"me=s-1 end="\v^\z1(\> ?)+"me=s-1

syn region	mailHeaderKey	contained contains=mailHeaderEmail,mailEmail,@mailQuoteExps start="\v(^(\> ?)*)@<=(to|b?cc):" skip=",$" end="$"
syn match	mailHeaderKey	contained contains=mailHeaderEmail,mailEmail "\v(^(\> ?)*)@<=(from|reply-to):.*$"
syn match	mailHeaderKey	contained "\v(^(\> ?)*)@<=date:"
syn match	mailSubject	contained "\v(^(\> ?)*)@<=subject:.*$"

" Anything in the header between < and > is an email address
syn match	mailHeaderEmail	contained "<.\{-}>"

" Mail Signatures. (Begin with "--", end with change in quote level)
syn region	mailSignature	contains=@mailLinks,@mailQuoteExps start="^\z(\(> \?\)*\)-- *$" end="^\z1$" end="^\z1\@!"me=s-1 end="^\z1\(> \?\)\+"me=s-1

" URLs start with a known protocol or www,web,w3.
syn match mailURL `\v<(((https?|ftp|gopher)://|(mailto|file|news):)[^' 	<>"]+|(www|web|w3)[a-z0-9_-]*\.[a-z0-9._-]+\.[^' 	<>"]+)[a-z0-9/]`
syn match mailEmail "\v[_=a-z\./+0-9-]+\@[a-z0-9._-]+\a{2}"

" Make sure quote markers in regions (header / signature) have correct color
syn match mailQuoteExp1	contained "\v^(\> ?)"
syn match mailQuoteExp2	contained "\v^(\> ?){2}"
syn match mailQuoteExp3	contained "\v^(\> ?){3}"
syn match mailQuoteExp4	contained "\v^(\> ?){4}"
syn match mailQuoteExp5	contained "\v^(\> ?){5}"
syn match mailQuoteExp6	contained "\v^(\> ?){6}"

" Even and odd quoted lines. order is imporant here!
syn match mailQuoted1	contains=mailHeader,@mailLinks,mailSignature "^\([a-z]\+>\|[]|}>]\).*$"
syn match mailQuoted2	contains=mailHeader,@mailLinks,mailSignature "^\(\([a-z]\+>\|[]|}>]\)[ \t]*\)\{2}.*$"
syn match mailQuoted3	contains=mailHeader,@mailLinks,mailSignature "^\(\([a-z]\+>\|[]|}>]\)[ \t]*\)\{3}.*$"
syn match mailQuoted4	contains=mailHeader,@mailLinks,mailSignature "^\(\([a-z]\+>\|[]|}>]\)[ \t]*\)\{4}.*$"
syn match mailQuoted5	contains=mailHeader,@mailLinks,mailSignature "^\(\([a-z]\+>\|[]|}>]\)[ \t]*\)\{5}.*$"
syn match mailQuoted6	contains=mailHeader,@mailLinks,mailSignature "^\(\([a-z]\+>\|[]|}>]\)[ \t]*\)\{6}.*$"

" Need to sync on the header. Assume we can do that within 30 lines
if exists("b:mail_minlines")
    exec "syn sync minlines=" . b:mail_minlines
else
    syn sync minlines=30	" All syntax groups are short
endif

" Define the default highlighting.
hi def link mailHeader		Statement
hi def link mailHeaderKey	Type
hi def link mailSignature	PreProc
hi def link mailHeaderEmail	mailEmail
hi def link mailEmail		Special
hi def link mailURL		String
hi def link mailSubject		LineNR
hi def link mailQuoted1		Comment
hi def link mailQuoted3		mailQuoted1
hi def link mailQuoted5		mailQuoted1
hi def link mailQuoted2		Identifier
hi def link mailQuoted4		mailQuoted2
hi def link mailQuoted6		mailQuoted2
hi def link mailQuoteExp1	mailQuoted1
hi def link mailQuoteExp2	mailQuoted2
hi def link mailQuoteExp3	mailQuoted3
hi def link mailQuoteExp4	mailQuoted4
hi def link mailQuoteExp5	mailQuoted5
hi def link mailQuoteExp6	mailQuoted6

let b:current_syntax = "mail"