-- ************************************************************************
--
--    Common Gateway Interface (CGI)
--    Copyright 2020 by Sean Conner.  All Rights Reserved.
--
--    This program is free software: you can redistribute it and/or modify
--    it under the terms of the GNU General Public License as published by
--    the Free Software Foundation, either version 3 of the License, or
--    (at your option) any later version.
--
--    This program is distributed in the hope that it will be useful,
--    but WITHOUT ANY WARRANTY; without even the implied warranty of
--    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
--    GNU General Public License for more details.
--
--    You should have received a copy of the GNU General Public License
--    along with this program.  If not, see <http://www.gnu.org/licenses/>.
--
--    Comments, questions and criticisms can be sent to: [email protected]
--
-- ************************************************************************
-- luacheck: ignore 611
-- RFC-3875, with some deviations for gopher

local syslog    = require "org.conman.syslog"
local errno     = require "org.conman.errno"
local fsys      = require "org.conman.fsys"
local process   = require "org.conman.process"
local exit      = require "org.conman.const.exit"
local mkios     = require "org.conman.net.ios"
local nfl       = require "org.conman.nfl"
local mklink    = require "port70.mklink"
local io        = require "io"
local coroutine = require "coroutine"

local require   = require
local pairs     = pairs
local ipairs    = ipairs

local DEVNULI = io.open("/dev/null","r")
local DEVNULO = io.open("/dev/null","w")

-- ************************************************************************

local function fdtoios(fd)
 local newfd = mkios()
 newfd.__fd  = fd
 newfd.__co  = coroutine.running()

 newfd.close = function(self)
   nfl.SOCKETS:remove(fd)
   self.__fd:close()
   return true
 end

 newfd._refill = function()
   return coroutine.yield()
 end

 nfl.SOCKETS:insert(fd,'r',function(event)
   if event.read then
     local data,err = fd:read(8192)
     if data then
       if #data == 0 then
         nfl.SOCKETS:remove(fd)
         newfd._eof = true
       end
       nfl.schedule(newfd.__co,data)
     else
       if err ~= errno.EAGAIN then
         syslog('error',"fd:read() = %s",errno[err])
       end
     end
   else
     newfd._eof = true
     nfl.SOCKETS:remove(fd)
     nfl.schedule(newfd.__co)
   end
 end)

 return newfd
end

-- ************************************************************************

return function(program,cinfo,request,ios)
 local conf = require "port70.CONF"

 if not conf.cgi then
   syslog('error',"CGI script %q called, but CGI not configured!",program)
   ios:write(mklink { type = 'error' , display = "Selector not found" , selector = request.selector })
   return false
 end

 local pipe,err1 = fsys.pipe()
 if not pipe then
   syslog('error',"CGI pipe: %s",errno[err1])
   ios:write(mklink { type = 'error' , display = "Selector not found" , selector = request.selector })
   return false
 end

 pipe.read:setvbuf('no') -- buffering kills the event loop

 local child,err2 = process.fork()

 if not child then
   syslog('error',"process.fork() = %s",errno[err2])
   ios:write(mklink { type = 'error' , display = "Selector not found" , selector = request.selector })
   return false
 end

 -- =========================================================
 -- The child runs off to do its own thang ...
 -- =========================================================

 if child == 0 then
   fsys.redirect(DEVNULI,io.stdin);
   fsys.redirect(pipe.write,io.stdout);
   fsys.redirect(DEVNULO,io.stderr);

   -- -----------------------------------------------------------------
   -- Close file descriptors that aren't stdin, stdout or stderr.  Most
   -- Unix systems have dirfd(), right?  Right?  And /proc/self/fd,
   -- right?  Um ... erm ...
   -- -----------------------------------------------------------------

   local dir = fsys.opendir("/proc/self/fd")
   if dir and dir._tofd then
     local dirfh = dir:_tofd()

     for file in dir.next,dir do
       local fh = tonumber(file)
       if fh > 2 and fh ~= dirfh then
         fsys._close(fh)
       end
     end

   -- ----------------------------------------------------------
   -- if all else fails, at least close these to make this work
   -- ----------------------------------------------------------

   else
     DEVNULI:close()
     DEVNULO:close()
     pipe.write:close()
     pipe.read:close()
   end

   local cwd      = conf.cgi.cwd
   local no_slash = conf.cgi.no_slash
   local args     = {}
   local env      = {}

   if conf.cgi.env then
     for var,val in pairs(conf.cgi.env) do
       env[var] = val
     end
   end

   if conf.cgi.instance then
     for name,info in pairs(conf.cgi.instance) do
       if request.rest:match(name) then
         if info.cwd then cwd = info.cwd end

         -- ---------------------------------------------------------------
         -- We want an instance no_slash to override a global no_slash, but
         -- if we can't just simply assign no_slash to the instance
         -- no_slash because if it doesn't exist, then it will set no_slash
         -- to false, possibly overriding the global var, which is NOT what
         -- is wanted here.  We need to check if the instance no_slash
         -- exists to properly override it.
         -- ---------------------------------------------------------------

         if type(info.no_slash) == 'boolean' then
           no_slash = info.no_slash
         end

         if info.arg then
           for i,arg in ipairs(info.arg) do
             args[i] = arg
           end
         end

         if info.env then
           for var,val in pairs(info.env) do
             env[var] = val
           end
         end
       end
     end
   end

   local _,e    = program:find(cinfo.directory,1,true)
   local script = e and program:sub(e+1,-1) or program

   if no_slash and script:match("^/") then
     script = script:sub(2,-1)
   end

   env.GOPHER_DOCUMENT_ROOT   = cinfo.directory
   env.GOPHER_SCRIPT_FILENAME = program
   env.GOPHER_SELECTOR        = request.selector .. request.rest
   env.GATEWAY_INTERFACE      = "CGI/1.1"
   env.QUERY_STRING           = request.search or ""
   env.REMOTE_ADDR            = request.remote.addr
   env.REMOTE_HOST            = request.remote.addr
   env.REQUEST_METHOD         = ""
   env.SCRIPT_NAME            = request.selector .. "/" .. script
   env.SERVER_NAME            = conf.network.host
   env.SERVER_PORT            = conf.network.port
   env.SERVER_PROTOCOL        = "GOPHER"
   env.SERVER_SOFTWARE        = "port70"

   _,e = request.rest:find(fsys.basename(program),1,true)
   local pathinfo = e and request.rest:sub(e+1,-1) or request.selector
   if pathinfo ~= "" then
     env.PATH_TRANSLATED = env.GOPHER_DOCUMENT_ROOT .. request.rest
     pathinfo            = pathinfo .. request.rest

     if no_slash and pathinfo:match("^/") then
       pathinfo = pathinfo:sub(2,-1)
     end

     env.PATH_INFO = pathinfo
   end

   if cwd then
     local okay,err3 = fsys.chdir(cwd)
     if not okay then
       syslog('error',"CGI cwd(%q) = %s",cwd,errno[err3])
       process.exit(exit.CONFIG)
     end
   end

   process.exec(program,args,env)
   process.exit(exit.OSERR)
 end

 -- =========================================================
 -- Meanwhile, back at the parent's place ...
 --
 -- NOTE: the CGI script is reponsible for sending the final '.' if the
 -- output is text.
 -- =========================================================

 pipe.write:close()
 local inp  = fdtoios(pipe.read)
 repeat
   local data = inp:read(1024)
   if data then ios:write(data) end
 until not data
 inp:close()

 local info,err4 = process.wait(child)

 if not info then
   syslog('error',"process.wait() = %s",errno[err4])
   return true,true
 end

 if info.status == 'normal' then
   if info.rc == 0 then
     return true,true
   else
     syslog('warning',"program=%q status=%d",program,info.rc)
     return true,true
   end
 else
   syslog('error',"program=%q status=%s description=%s",program,info.status,info.description)
   return true,true
 end
end

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