#!/bin/sh
# hand off to tcl
# The backslash makes the next line a comment in Tcl \
exec tclsh "$0" ${1+"$@"}

# program to control OpenACS servers with daemontools and balance
# This script assumes:
#   1. all affected OpenACS servers are listed as files in live_dir 
#      or standby_dir
#   a. The name of each file is the servername
#   b. The content of each file is the port number of the server,
#      which does not change
#   3. all affected servers have config.tcl files that know to look
#      in live_dir to adjust themselves accordingly
#   4. daemontools controls each server at /service/servicename

######################################################################
# parameters
######################################################################

# TODO: this should become a passed-in parameter
set system_name cnet
set live_port 8080

set stem $system_name
set balance_bin /usr/sbin/balance
set daemon_bin /usr/local/bin/svc
set web_base /var/lib/aolserver
set shared_dir $web_base/$stem
set live_dir $shared_dir/etc/live
set standby_dir $shared_dir/etc/standby

######################################################################
# initialization
######################################################################

set help_p false
set status_p false
set status_plus_p false
set switch_p false
set last_flag ""
set promote ""
set demote ""

#----------------------------------------------------------------------
# process command line arguments
#----------------------------------------------------------------------

# accepting only two arguments
set switch [lindex $argv 0]
set arg1 [lindex $argv 1]

switch -glob -- $switch {
    status  {
	set status_p true
    }
    statusplus  {
	set status_p true
	set status_plus_p true
    }
    help    {set help_p true}
    version {set help_p true}
    switch  {set switch_p true}
    demote  {if {$arg1 ne "" } {
                     set demote $arg1
                 } {
		     set help_p true
		 }
    }
    promote  {if {$arg1 ne "" } {
                     set promote $arg1
                 } {
		     set help_p true
		 }
    }
    default  {set help_p true}
}

#----------------------------------------------------------------------
# Inspect the results of balance
#----------------------------------------------------------------------

if { ![catch {set balance_txt [exec $balance_bin -c show 80] } result] } {
    # pluck out the channel data from balance:
    #  0   RR  0 dis        127.0.0.1  8001
    #         ^^ ^^^                  ^^^^^
    #01234567890123456789012345678901234567890
    #          1         2         3
    set channel_data [list]
    set channel_fodder $balance_txt
    while {[regexp {(.[^\n]+)} $channel_fodder match_fodder row] } {
	# remove each row as it's handled
	set remove_count [string length $row]
	set channel_fodder [string range $channel_fodder [expr {$remove_count + 1}] end]
	set channel [string range $row 9 10]
	set port [string range $row 33 37]
	set status [string range $row 12 14]
	lappend channel_data [list [string trim $port] [string trim $channel] [string trim $status]]
    }
} else {
    puts "Error checking status: $result"
    exit
}
    
#----------------------------------------------------------------------
# inspect list_dir and standby_dir
#----------------------------------------------------------------------
# get a list of files and their contents in each of the live and
# standby dirs
# serverlist: 
#   0 servername (foo-a, foo-b, ...)
#   1 port (8001, 8002, ...)
#   2 channel (0, 1, ...)
#   3 status  (dis, ENA)
#   4 type (live, standby)

set server_list [list]
foreach type {live standby} {
    set dir ${type}_dir
    if { [catch {set files [exec ls [set $dir]] } result] } {
	puts  "Error checking $type list: $result"
	exit
    }

    foreach file $files {
	if { [catch {set fileId [open "[set $dir]/$file"]} result] } {
	    puts "Error reading $dir/$file"
	    continue
	} else {
	    set file_contents [string trim [read $fileId] ]	
	    close $fileId
	}

	if { $file_contents ne "" } {
	    set channel_match [lsearch -regexp $channel_data $file_contents ]
	    if { $channel_match >= 1 } {
		set channel_info [lindex $channel_data $channel_match]
		set channel [lindex $channel_info 1]
		set status  [lindex $channel_info 2]
	    } else {
		set channel "unknown"
	    }
	    lappend server_list [list $file $file_contents $channel $status $type]
	}
    }
}

######################################################################
# Procedure Library
######################################################################

#----------------------------------------------------------------------
# Help
#----------------------------------------------------------------------

proc help {}  {
    puts  {Usage: deploy
	status         status report
	help           this message
	switch         if there is one live server and one standby server, exchange them 
	demote server  move server from live to standby
	promote server move server from standby to live
    }
}

#----------------------------------------------------------------------
# status report, Mr Sulu
#----------------------------------------------------------------------
proc status {plus_p} {
    global server_list
    global balance_txt

    puts  ""
    puts  "type    |   server      | port|channel|             status"
    #      0123456789012345678901234567890123456789012345678901234567890123456789
    puts  "---------------+--------+-----+-------+-------------------------------"

    foreach file $server_list {
	set balance_status [lindex $file 3]
	set type [lindex $file 4]
	set should_be [string map { 
  	    live    ENA
	    standby dis
	} $type]

	if {$balance_status eq $should_be} {
	    set status OK
	} else {
	    set status "PROBLEM: is $balance_status, should be $should_be"
	}

	set    output [format %-8.8s   $type]|
 	append output [format %15.15s  [lindex $file 0]]|
	append output [format %5.5s    [lindex $file 1]]|
	append output [format %7.7s    [lindex $file 2]]|
	append output [format %30.30s $status]
	puts $output
    }

    puts ""

    if {$plus_p} {
	puts "Additional information:"
	puts  $balance_txt
	puts  ""
    }
	
}

#----------------------------------------------------------------------
# demote
#----------------------------------------------------------------------

proc demote {server} {
    global server_list
    global web_base
    global stem
    global standby_dir
    global live_dir
    global balance_bin

    set demote_server [lindex $server_list [lsearch -regexp $server_list $server]]
    if { [lindex $demote_server 4] ne "live" } {
	puts "$server is not a live server - cannot demote"
	exit
    }
    set channel [lindex $demote_server 2]

    puts "Demoting $server"

    if { [catch {
	exec rm $web_base/${stem}-standby
	exec ln -s $web_base/$server $web_base/${stem}-standby
	exec mv $live_dir/$server $standby_dir
	exec $balance_bin -c "disable $channel" 80
    } result] } {
	puts "Error demoting $server: $result"
    } else {
	puts "Successfully demoted $server"
    }
}

#----------------------------------------------------------------------
# promote
#----------------------------------------------------------------------

proc promote {server} {
    global server_list
    global web_base
    global stem
    global standby_dir
    global live_dir
    global balance_bin

    set promote_server [lindex $server_list [lsearch -regexp $server_list $server]]
    if { [lindex $promote_server 4] ne "standby" } {
	puts "$server is not a standby server - cannot promote"
	exit
    }
    set channel [lindex $promote_server 2]

    puts "Promoting $server (channel $channel)"

    if { [catch {
	exec rm $web_base/${stem}-live
	exec ln -s $web_base/$server $web_base/${stem}-live
	exec mv $standby_dir/$server $live_dir
	exec $balance_bin -c "enable $channel" 80 
    } result] } {
	puts "Error promoting $server: $result"
    } else {
	puts "Successfully promoted $server"
    }
}

######################################################################
# execution body
######################################################################

if { $help_p } {
    help
    exit
}

if { $status_p } {
    status $status_plus_p
    exit
}

if { $demote ne "" } {
    demote $demote
    exit
}

if { $promote ne "" } {
    promote $promote
    exit
}

if { $switch_p } {
    # TODO: should check here to make sure there's one live and one standby

    set standby_server [lindex $server_list [lsearch -regexp $server_list standby]]
    set promote_channel [lindex $standby_server 2]
    set promote [lindex $standby_server 0]
    
    set live_server [lindex $server_list [lsearch -regexp $server_list live]]
    set demote_channel [lindex $live_server 2]
    set demote [lindex $live_server 0]
    
    promote $promote
    demote $demote
    puts "Promoted $promote and demoted $demote"
    exit
}

# not sure how we got here
help
exit