#!/usr/bin/env bash
# raid.sh - Pure RAID-level logic (testable, no I/O).
# Source after common.sh.

#############################
# Valid-level enumeration
#############################

# Print valid RAID levels for a given disk count, one per line.
# Count <2: nothing printed (single disk = no RAID).
# Count 2:  mirror, stripe
# Count 3+: + raidz1
# Count 4+: + raidz2
# Count 5+: + raidz3
raid_valid_levels_for_count() {
    local count=$1
    [[ $count -lt 2 ]] && return 0
    echo mirror
    echo stripe
    [[ $count -ge 3 ]] && echo raidz1
    [[ $count -ge 4 ]] && echo raidz2
    [[ $count -ge 5 ]] && echo raidz3
    return 0
}

# Return 0 if level is valid for the given disk count, 1 otherwise.
# Empty level with count 1 is valid (no RAID).
raid_is_valid() {
    local level=$1 count=$2
    if [[ $count -le 1 ]]; then
        [[ -z "$level" ]]
        return
    fi
    raid_valid_levels_for_count "$count" | grep -qxF "$level"
}

#############################
# Usable-space computation
#############################

# Print usable bytes for a level given disk count, smallest-disk bytes,
# and total bytes across all disks. Writes nothing and returns 1 for
# unknown levels.
#
# Usage: raid_usable_bytes LEVEL COUNT SMALLEST_BYTES TOTAL_BYTES
raid_usable_bytes() {
    local level=$1 count=$2 smallest=$3 total=$4
    case "$level" in
        mirror)  echo "$smallest" ;;
        stripe)  echo "$total" ;;
        raidz1)  echo $(( (count - 1) * smallest )) ;;
        raidz2)  echo $(( (count - 2) * smallest )) ;;
        raidz3)  echo $(( (count - 3) * smallest )) ;;
        *)       return 1 ;;
    esac
}

# Print fault-tolerance (max number of disks that can fail) for a level
# at the given disk count. Unknown level → return 1.
raid_fault_tolerance() {
    local level=$1 count=$2
    case "$level" in
        mirror)  echo $(( count - 1 )) ;;
        stripe)  echo 0 ;;
        raidz1)  echo 1 ;;
        raidz2)  echo 2 ;;
        raidz3)  echo 3 ;;
        *)       return 1 ;;
    esac
}