Protohackers primality

downstream

#!/bin/bash

debug() {
  echo "$@" >&2
}

while IFS= read -r line || [[ -n "$line" ]]
do
  req="$(<<<"$line" jq -c .)"
  debug "input: $req"
  if [[ $? != 0 ]]; then
    debug "  malformed json"
    echo '{}'
    exit
  fi

  wellformed="$(<<<"$req" jq -c '
    (.method == "isPrime") and (.number | type == "number")
  ')"
  if [[ "$wellformed" != true ]]; then
    debug "  not well formed"
    echo '{}'
    exit
  fi

  debug "  well formed"
  number="$(<<<"$req" jq -c '
    def isInteger:
      (. | type == "number") and
      (. | floor == .)
    ;
    if (.number | isInteger) and (.number > 1) then
      .number
    else
      0
    end
  ')"

  prime="$(openssl prime -- "$number" | grep -v 'is not')"

  if [[ -n "$prime" ]]; then
    debug "  prime: $number"
    echo '{"method": "isPrime", "prime": true}'
  else
    debug "  not prime: $number"
    echo '{"method": "isPrime", "prime": false}'
  fi

done

listen

#!/bin/sh

socat TCP-LISTEN:12345,fork,reuseaddr EXEC:./downstream

NOTE

This has a performance problem with the multiclient tests on the host I run it on.

I initially used an alternative jq-only naive primality test - this was too slow as well, so I dropped into openssl's checker.
```
# replace from `number=`
<<<"$req" jq -c '
    def isInteger:
      (. | type == "number") and
      (. | floor == .)
    ;
    def isFactor($f):
      if $f * $f > . then
        false
      elif . % $f == 0 then
        true
      else
        isFactor($f + 1)
      end
    ;
    def isPrime:
      if . < 2 then
        false
      else
        isFactor(2)
      end
    ;
    { method: "isPrime",
      prime: ((.number | isInteger) and (.number | isPrime)) }
  '
```