#!/bin/bash

# CLOUD_IMG: This file was created/modified by the Cloud Image build process
# For Oracle Cloud Infrastructure persistent device naming
# Author: Oracle

# Script to create symlinks in devices that is based on LUN IDs.
# Link vda always points to the root device.
# This script works only for iSCSI attachments

# If the number of parameters being sent to this script is not equal to 1,
# we throw an error. We expect the kernel device name like "sda", "sdb" etc.
if [ "$#" -ne 1 ]; then
    echo "Unexpected number of inputs ($@). Usage: cmd <device>" >&2
    exit 1
fi

if [[ "$DEVPATH" = *"virtio"* ]]; then
    # Using ID_PATH to retrieve the LU #
    # ID_PATH is virtio-pci-0000:00:04.0-scsi-0:0:2:12
    # With the substitution, we would be able to get 12 which is the LUN number.
    LUN=$(echo "$ID_PATH" | sed 's/.*://')
else
    # Using DEVPATH to retrieve the LUN #
    # DEVPATH is /devices/platform/host5/session3/target5:0:0/5:0:0:12/block/sdc
    # With first substitution, the string becomes 12/block/sdc
    # With second substitution, the string becomes 12/
    # With third substitution, the last character is removed and we are able to retrieve
    # the LUN number which is 12.
    LUN=$(echo "$DEVPATH" | sed 's/.*://' | sed 's/\([/]\).*/\1/' | sed s'/.$//')
fi

if [ x"$LUN" = "x" ]; then
    echo "Unable to determine LUN for $DEVPATH" >&2
    exit 1
fi

# We can use ID_PATH to figure out iSCSI boot volumes
# ID_PATH is ip-169.254.0.2:3260-iscsi-iqn.2015-02.oracle.boot:uefi-lun-1
# After the substitution, we get uefi-lun-1
BOOTLUN=${ID_PATH//.*://}
#BOOTLUN=$(echo "$ID_PATH" |sed 's/.*://')
# iSCSI boot volumes are recognized with uefi-lun-1
if [[ "$BOOTLUN" = *"uefi-lun-1"* ]]; then
    echo "$1" | sed 's#sd[a-z]*[a-z]#oracleoci/oraclevda#g'
    exit 0
fi

# In case of PV Boot volume, the ID_PATH is virtio-pci-0000:00:04.0-scsi-0:0:0:1
# By applying the substitution, we get the LUN number as 1 
# 1 is special case reserved for boot volumes.
if [ "$BOOTLUN" = "1" ]; then
    echo "$1" | sed 's#sd[a-z]*[a-z]#oracleoci/oraclevda#g'
    exit 0
fi

# Test to ensure $LUN is a number
re='^[0-9]+$'
if ! [[ "$LUN" =~ $re ]] ; then
    echo "LUN ($LUN) is not a number" >&2
    exit 1
fi

# We allow a maximum device name to be vdzz - corresponding to LUN=702 (26 + (26 * 26))
if [ "$LUN" -gt "702" ]; then
    echo "LUN value ($LUN) exceeds maximum range" >&2
    exit 1
fi

# We don't allow the LUN # to be less than 1
if [ "$LUN" -le "0" ]; then
    echo "LUN value ($LUN) lower than one" >&2
    exit 1
fi

# Converts a number to ASCII char
chr() {
    printf \\$(printf '%03o' "$1")
}

# Construct a one- or two-letter suffix using the LUN ID.
# 2 means vdb, 3 means vdc and so on
# 27 means vdaa and so on.
LETTER1=$((LUN/26))
LETTER2=$(((LUN - (LETTER1 * 26)) % 26))

if [ "$LETTER2" -eq 0 ]; then
    LETTER2='z'
      if [ "$LETTER1" -eq 1 ]; then
            LETTER1=''
      else
            LETTER1=$(chr $((LETTER1 + 95)))
      fi
else
    LETTER2=$(chr $((LETTER2 + 96)))
    if [ "$LETTER1" -eq 0 ]; then
            LETTER1=''
      else
            LETTER1=$(chr $((LETTER1 + 96)))
      fi
fi

# Suffix is one or two letters and depends on value of LUN number
# in the range [1:702] inclusive
SUFFIX="$LETTER1$LETTER2"

echo "$1" | sed "s#sd[a-z]*[a-z]#oracleoci/oraclevd$SUFFIX#g"
exit 0