#!/bin/sh
# vim:set ft=tcl: \
exec tclsh "$0" "$@"

# require Tcl version of at least 8.5 since I use 'ni' and 'in' in expressions for lists
package require Tcl 8.5
package require sqlite3

if { $argc < 1 } {	
	puts {Populates photo cache directory for users from the database}
	puts {Usage:}
	puts "  $argv0 database_filename"
	puts {}
	puts {Example:}
	puts "  $argv0  2013_Spring_Phys742"
	exit
}

set dbfile [lindex $argv 0] 

source ./GradeBook_lib.tcl

set config_file "./gb_config.tcl"
if { [file exists $config_file] && ("$config_file" ne "") } {
	source $config_file
} else {
	puts "error: config file {$config_file} does not exist"
	exit
}

if { [file exists $dbfile] } {
	sqlite3 db $dbfile
} else {
	puts "error: non existing DB filename {$dbfile}"
	exit
}

proc getAllIds {ids_col table_with_ids} {
	set ids {}
	set eval_str "SELECT \"$ids_col\"  FROM \"$table_with_ids\""
	set err [catch {
		db eval $eval_str v {
			if { [info exist v($ids_col)] } {	
				lappend ids $v($ids_col)
			} 
		}
	} errStat ]
	if { $err } {
		puts  "the following error happen: $errStat" msg_level_critical
	} 
	return $ids
}

proc cachePhotoForId { IdNum } {
	# attempt to cache the photo for a given id
	global GradebookServerConfig
	set photo_album_base_url $GradebookServerConfig(photo_album_base_url)
	set photo_album_cache $GradebookServerConfig(photo_album_cache)

	# generate url pointing to a photo of a user with the given IdNum
	set photo_file "${IdNum}.jpg"
	set cached_photo_file "$photo_album_cache/${photo_file}"
	set url "$photo_album_base_url/$photo_file"

	if { [file exists "$cached_photo_file"] } {
		# file already cached no need to download
		return
	}
	if { ![file exists "$photo_album_cache"] } {
		# cache directory missing let's make it
		set errMkDir [catch {
			file mkdir "$photo_album_cache"
		} errStat ]
		if { $errMkDir } {
			puts  "Error: $errStat"
			return
		}
	}
	
	# Download url to cache
	
	# below replacing whitespace with %20 and # with %23 in the URL in $target
	set url [string map {{ } %20 {#} %23 } $url]
	set command_str exec
	lappend command_str wget
	lappend command_str -q
	lappend command_str -c
	lappend command_str --output-document=$cached_photo_file
	lappend command_str $url
	# TODO: devise some sort of lock mechanism to protect against duplicate downloads
	set err [catch {eval $command_str} result]
	if { $err } {
		puts "Something wrong with download of {$url}"
		# remove erroneous download file
		file delete $cached_photo_file
	} else {
		puts "Successful download of {$url}"
	}
}

set table_with_ids GradesTable
set ids_col IdNum
if { ![doesColumnExists $ids_col $table_with_ids] } {
	puts "something wrong with database: the column {$ids_col} does not exist in table {$table_with_ids}"
	db close
	exit
}

set ids [getAllIds "$ids_col" "$table_with_ids"]
foreach id  $ids {
	if { "$id" eq "" } {
		# invalid/useless id
		continue
	}
	cachePhotoForId $id
}

db close

# vim: ts=2 sw=2 foldmethod=indent: