--/makedoc title Documentation for version.e v0.2.

--/topic Information
--/info
-- version.e enables code to decide what is the current interpreter version, 
-- without outside assistance or knowledge.
-- Version 0.1 was released Feb 15, 2007.
-- Version 0.2 has more comments and auxilliary functions to recognise and set the 
-- default string returned instead of the actual interpreter version. Should 
-- also succeed under more adverse conditions.
-- Version 0.3 released Feb 20,2007 tries harder to guess the installation folder.
--
-- DISCLAIMER - TERMS OF USE
--
-- The software is provided as-is. The author can not be held responsible for anything 
-- resulting from the use of the current software.
-- Permission is granted to freely distribute the code. 
-- Modifying the code and releasing it is allowed under the provision that 
--/li the original author is adequately represented as such.
--/li each alteration is clearly marked as such.

--/topic Authors
--/info
-- CChris ~<oedoc@free.fr>

sequence s

-- At your discretion, you may use the file as is, or
-- uncomment the include statement and comment the constants and function below.

--include get.e

sequence s
constant GET_EOF=-1,CHUNK=100
function get_bytes(integer fn, integer n)
-- Copied from RDS' official get.e standard include file.
-- so as to avoid the hassles of including files etc    
    integer c, first, last
    sequence s
    
    if n = 0 then
    	return {}
    end if
    
    c = getc(fn)
    if c = GET_EOF then
    	return {}
    end if
    
    s = repeat(c, n)
    
    last = 1
    while last < n do
	-- for speed, read a chunk without checking for EOF
    	first = last+1
    	last  = last+CHUNK
    	if last > n then
    	    last = n
    	end if
    	for i = first to last do
    	    s[i] = getc(fn)
    	end for
    	-- check for EOF after each chunk
    	if s[last] = GET_EOF then  
    	    -- trim the EOF's and return
    	    while s[last] = GET_EOF do
        		last -= 1
    	    end while 
    	    return s[1..last]
    	end if
    end while   
    return s
end function

integer slash,separator
sequence default
if platform()>WIN32 then
    slash='/'
    separator=':'
    default="/$HOME/usr/euphoria/"
else
    slash='\\'
    separator=';'
    default="C:\\EUPHORIA\\"
end if

sequence notAVersion
notAVersion="0.0.0"

--/topic Version Info
--/func setNotAVersion(object s)
--/desc Possibly sets the string returned when the version is not available.
--/ret (SEQUENCE) The current string used to signal failure to determine interpreter version.
-- If /i s is an atom, the current value will be returned and kept unchanged.
global function setNotAVersinon(object s)
    sequence oldVal
    
    oldVal=notAVersion
    if sequence(s) then
        notAVersion=s
    end if
    return notAVersion
end procedure

--/topic Version Info
--/func  isAVersion(sequence s)
--/desc Tells whether a string signals reckon to establish corrent interpreter version.
--/ret (INTEGER) 1 if the string is a version string, else 0.
-- Use this function to interpret the value returned by /getEuVersion().
global function isAVersion(sequence s)
    return compare(s,notAVersion)!=0
end function

--/topic Version Info
--/func getEuVersion()
--/desc Returns a string, the version of the Euphoria interpreter used to run this file.
--/ret (SEQUENCE) A version strong, or /notAVersion if unavailable or irrelevant.
-- Bound or translated programs return /notAVersion. Programs executed from spurce 
-- might return "2.3" , "3.0.1", etc. If the version isn't reckoned, the function 
-- returns a default string (initially "0.0.0"). Use /isAVersion() to check
-- whether this string is returned, and /setNotAVersion() to get or zset it.
global function getEuVersion()
    integer p,q
    sequence s1,s2 
    object x
    
    s=command_line()
    if not compare(s[1],s[2]) then 
    -- the program is not running as source code, hence this is not needed
        return notAVersion
    end if
    s=s[1]
    -- figure the Euphoria installation folder from the environment.
    -- If this fails, ...
    x=getenv("EUDIR")
    if sequence(x) then
        s1=x&slash
        p=length(s1)
    else  -- try looking in the include standard folder
        x=getenv("EUINC")
        if sequence(x) then
            s1=x
            p=length(s1)
        else
            s1=s
            p=find(slash,s1)
            if p=0 then
            --  executable was found, but no explicit path
                x=getenv("PATH") 
                if sequence(x) then
                    s1=x
                else
                    s1=""
                end if
                while 1 do
                    p=find(separator,s1)
                    if p=0 then -- no path, or path sequence exhausted
                        s1={'.',slash} -- try current dir
                        exit
                    else
                        s2=s1[1..p-1]
                        q=open(s2&slash&s,"r")  -- faster than a dir()
                        if q!=-1 then
                            close(q)
                            s1=s2
                            exit
                        else
                            s1=s1[p+1..length(s1)]
                        end if
                    end if
                end while
            end if
            p=length(s1)
            while p>0 and s1[p]!=slash do 
                p-=1 
            end while
            p-=1
        end if    
        while p>0 and s1[p]!=slash do 
            p-=1 
        end while
    end if
    s1=s1[1..p]&"readme.htm"
    if s1[1]='\"' then   -- quoted path
        s1&='\"'
    end if 
    p=open(s1,"rb")
    if p=-1 then  -- the best guess didn't work, try platform-dependent defaults
        p=open(default,"rb")
        if p=-1 then
            return notAVersion
        end if
    end if
    q=machine_func(19,{p,1600})  -- seek()
    if q=0 then
        return notAVersion
    end if
    s1=get_bytes(p,200) -- get a chunk from the file
                        -- hopefully its header didn't change much over the years
    close(p)
    p=match("version ",s1)  
    if p>0 then -- return version string
        s1=s1[p+8..length(s1)]
        p=match("<br>",s1)
        return s1[1..p-1]
    else 
        return notAVersion
    end if
end function