#!/usr/bin/env bash
#=== HELP START ===
# convert-md-tree.sh – Recursive Markdown → HTML conversion (Pandoc)
#
# Usage:
#   ./convert-md-tree.sh [options] <source_dir> <dest_dir>
#
# Options:
#   -n, --dry-run               Show what would be done without converting
#   -p, --pandoc-args <string>  Extra arguments passed to pandoc (e.g. "-t html5")
#   -h, --help                  Show this help message
#
# Arguments:
#   <source_dir>                Root directory containing .md files
#   <dest_dir>                  Destination directory for the HTML output
#
# Behaviour:
#   • Preserves the directory structure in the destination.
#   • Creates required sub-directories automatically.
#   • Emits clear errors for missing programs or invalid parameters.
#=== HELP END ===
set -euo pipefail

# ───────────────────────────────────────────────
# Defaults
DRY_RUN=false
PANDOC_ARGS=""
# ───────────────────────────────────────────────

# 0 Help function -------------------------------------------------------------
show_help() {
  sed -n '/^#=== HELP START ===/,/^#=== HELP END ===/ {
    /^#=== HELP START ===/d
    /^#=== HELP END ===/d
    s/^#//
    p
  }' "$0"
}

# 1 Parse options -------------------------------------------------------------
POSITIONAL=()
while [[ $# -gt 0 ]]; do
  case "$1" in
    -h|--help) show_help; exit 0 ;;
    -n|--dry-run) DRY_RUN=true; shift ;;
    -p|--pandoc-args)
      [[ $# -lt 2 ]] && { echo "❌ Option $1 requires an argument"; exit 1; }
      PANDOC_ARGS="$2"; shift 2 ;;
    --) shift; break ;;
    -*)
      echo "❌ Unknown option: $1"; exit 1 ;;
    *) POSITIONAL+=("$1"); shift ;;
  esac
done
set -- "${POSITIONAL[@]}"

[[ $# -lt 2 ]] && { echo "❌ Missing <source_dir> and/or <dest_dir>"; echo; show_help; exit 1; }

SRC="$1"
DEST="$2"

# 2 Validate arguments --------------------------------------------------------
[[ ! -d "$SRC" ]] && { echo "❌ Source directory does not exist: $SRC"; exit 1; }

mkdir -p "$DEST" || { echo "❌ Cannot create/access dest dir: $DEST"; exit 1; }

# Remove trailing slash for path manipulation
SRC="${SRC%/}"

# 3 Check required tools ------------------------------------------------------
need() { command -v "$1" >/dev/null || { echo "❌ $1 is missing"; exit 1; }; }
need pandoc; need find; need mkdir

# 4 Process files -------------------------------------------------------------
echo "🔍 Scanning for .md files in $SRC …"
COUNT_TOTAL=$(find "$SRC" -type f -name '*.md' | wc -l | tr -d ' ')
[[ "$COUNT_TOTAL" -eq 0 ]] && { echo "ℹ️  No Markdown files found – nothing to do."; exit 0; }
echo "📄 Found $COUNT_TOTAL Markdown file(s)."

CONVERTED=0
while IFS= read -r -d '' FILE; do
  REL_PATH="${FILE#$SRC/}"
  OUT_FILE="$DEST/${REL_PATH%.md}.html"
  mkdir -p "$(dirname "$OUT_FILE")"

  if $DRY_RUN; then
    echo "🧪 Would convert: $FILE -> $OUT_FILE"
  else
    pandoc $PANDOC_ARGS "$FILE" -s -o "$OUT_FILE"
    echo "✅ Converted: $FILE -> $OUT_FILE"
  fi
  ((CONVERTED++))
done < <(find "$SRC" -type f -name '*.md' -print0)

if $DRY_RUN; then
  echo "🧪 Dry-run complete – $CONVERTED file(s) would be processed."
else
  echo "🏁 Finished – $CONVERTED file(s) converted."
fi