#!/usr/bin/env bash
set -euo pipefail

ROOT="."
declare -a SKIP_DIRS=()
declare -a PATTERNS=()

usage() {
  cat <<EOF
Usage: $0 [-r root_dir] [-s dir_to_skip]... -p pattern ...

Options:
  -r DIR       Root directory (default: .)
  -s DIR       Directory name to skip (can repeat)
  -p PATTERN   File pattern (e.g. '*.md', '*.txt') (required, can repeat)

Example:
  $0 -p '*.md'
  $0 -r src -s node_modules -s .git -p '*.md' -p '*.txt'
EOF
  exit 1
}

while getopts ":r:s:p:" opt; do
  case "$opt" in
    r) ROOT="$OPTARG" ;;
    s) SKIP_DIRS+=("$OPTARG") ;;
    p) PATTERNS+=("$OPTARG") ;;
    *) usage ;;
  esac
done

shift $((OPTIND - 1))

# Require at least one pattern
(( ${#PATTERNS[@]} > 0 )) || usage

# Build prune expression
PRUNE_EXPR=()
if (( ${#SKIP_DIRS[@]} > 0 )); then
  PRUNE_EXPR+=( \( )
  for i in "${!SKIP_DIRS[@]}"; do
    PRUNE_EXPR+=( -type d -name "${SKIP_DIRS[$i]}" -prune )
    [[ $i -lt $((${#SKIP_DIRS[@]} - 1)) ]] && PRUNE_EXPR+=( -o )
  done
  PRUNE_EXPR+=( \) -o )
fi

# Build pattern expression
PATTERN_EXPR=( \( )
for i in "${!PATTERNS[@]}"; do
  PATTERN_EXPR+=( -name "${PATTERNS[$i]}" )
  [[ $i -lt $((${#PATTERNS[@]} - 1)) ]] && PATTERN_EXPR+=( -o )
done
PATTERN_EXPR+=( \) )

# Execute
find "$ROOT" \
  "${PRUNE_EXPR[@]}" \
  -type f \
  "${PATTERN_EXPR[@]}" \
  -print0 |
while IFS= read -r -d '' file; do
  printf "\n===== %s =====\n" "$file"
  cat "$file"
done