## system handle table: file open/read/write/close and the validation gate

fun chk(ok msg) {
	if ok { printf "OK: %s\n" msg } \
	else { printf "ERROR: %s\n" msg }
}

path := "/tmp/hak-hnd-01.tmp"

## --- write ---
h := (sys.open path "w")
chk (integer? h) "sys.open for write returns a handle id"

buf := (core.basicNew ByteArray 5)
core.basicAtPut buf 0 104
core.basicAtPut buf 1 101
core.basicAtPut buf 2 108
core.basicAtPut buf 3 108
core.basicAtPut buf 4 111
chk (= (sys.write h buf) 5) "sys.write returns the byte count"
sys.close h

## --- read it back ---
h := (sys.open path "r")
rb := (core.basicNew ByteArray 16)
n := (sys.read h rb)
chk (= n 5) "sys.read returns the byte count"
chk (= (core.basicAt rb 0) 104) "first byte round-tripped"
chk (= (core.basicAt rb 4) 111) "last byte round-tripped"
chk (= (sys.read h rb) 0) "sys.read at end of file returns 0"

## --- offset and length ---
sys.close h
h := (sys.open path "r")
zb := (core.basicNew ByteArray 16)
chk (= (sys.read h zb 2 3) 3) "sys.read honours offset and length"
chk (= (core.basicAt zb 0) 0) "bytes before the offset are untouched"
chk (= (core.basicAt zb 2) 104) "data landed at the offset"
sys.close h

## --- close returns nil ---
h := (sys.open path "r")
chk (nil? (sys.close h)) "sys.close returns nil"

## --- a fresh handle reuses the freed id ---
h2 := (sys.open path "r")
chk (integer? h2) "a handle id is handed out again after a close"
sys.close h2