#!/usr/bin/env bash
# migrate-brain-halls.sh — move flat brain/wiki/{concepts,entities}/ notes
# into the structured brain/wiki/<wing>/<hall>/ layout introduced by
# hyperguild#1.
#
# Reads each note's YAML frontmatter:
#   type:   maps to hall (decision, hypothesis, failure, source → eponymous;
#           concept, entity, anything else → facts)
#   domain: maps to wing (sanitised: lowercase, alphanumerics + hyphens);
#           empty → "general"
#
# Dry-run by default. Pass --commit to actually move files. Idempotent:
# already-migrated notes (already under a Wing dir) are left alone.
#
# Usage:
#   scripts/migrate-brain-halls.sh /path/to/brain            # dry-run
#   scripts/migrate-brain-halls.sh --commit /path/to/brain   # apply

set -euo pipefail

COMMIT=0
BRAIN=""
for arg in "$@"; do
  case "$arg" in
    --commit) COMMIT=1 ;;
    -h|--help)
      sed -n '2,18p' "$0"
      exit 0
      ;;
    *) BRAIN="$arg" ;;
  esac
done

if [[ -z "$BRAIN" ]]; then
  echo "error: brain directory required" >&2
  echo "usage: $0 [--commit] <brain-dir>" >&2
  exit 2
fi

if [[ ! -d "$BRAIN" ]]; then
  echo "error: $BRAIN is not a directory" >&2
  exit 2
fi

WIKI="$BRAIN/wiki"
if [[ ! -d "$WIKI" ]]; then
  echo "no $WIKI/ — nothing to migrate"
  exit 0
fi

sanitise() {
  # lowercase, replace non-alnum with hyphen, collapse hyphens, trim
  local s
  s=$(printf '%s' "$1" | tr '[:upper:]' '[:lower:]' \
        | sed -E 's/[^a-z0-9]+/-/g; s/^-+//; s/-+$//; s/-+/-/g')
  printf '%s' "$s"
}

# extract_frontmatter_value <file> <key>
# Echoes the value (trimmed, unquoted) of `key:` from a leading YAML
# frontmatter block. Empty if absent or no frontmatter.
extract_frontmatter_value() {
  awk -v key="$2" '
    BEGIN { in_fm = 0; first = 1 }
    /^---[[:space:]]*$/ {
      if (first) { in_fm = 1; first = 0; next }
      if (in_fm) { exit }
    }
    in_fm {
      idx = index($0, ":")
      if (idx == 0) next
      k = substr($0, 1, idx-1)
      v = substr($0, idx+1)
      gsub(/^[[:space:]]+|[[:space:]]+$/, "", k)
      gsub(/^[[:space:]]+|[[:space:]]+$/, "", v)
      gsub(/^["'\'']|["'\'']$/, "", v)
      if (k == key) { print v; exit }
    }
  ' "$1"
}

hall_for_type() {
  case "$1" in
    decision|decisions)   echo "decisions" ;;
    hypothesis|hypotheses) echo "hypotheses" ;;
    failure|failures)     echo "failures" ;;
    source|sources)       echo "sources" ;;
    *)                    echo "facts" ;;
  esac
}

declare -i moved=0 skipped=0

migrate_source_dir() {
  local src="$1"
  [[ -d "$src" ]] || return 0
  while IFS= read -r -d '' f; do
    local typ domain wing hall slug dest
    typ=$(extract_frontmatter_value "$f" type)
    domain=$(extract_frontmatter_value "$f" domain)
    hall=$(hall_for_type "$typ")
    wing=$(sanitise "${domain:-general}")
    [[ -z "$wing" ]] && wing="general"
    slug=$(basename "$f" .md)
    dest="$WIKI/$wing/$hall/$slug.md"

    if [[ "$f" == "$dest" ]]; then
      skipped=$((skipped + 1))
      continue
    fi

    if [[ -e "$dest" ]]; then
      echo "skip (target exists): $f → $dest"
      skipped=$((skipped + 1))
      continue
    fi

    if [[ "$COMMIT" -eq 1 ]]; then
      mkdir -p "$(dirname "$dest")"
      git -C "$BRAIN" mv "$f" "$dest" 2>/dev/null || mv "$f" "$dest"
    fi
    echo "move: $f → $dest"
    moved=$((moved + 1))
  done < <(find "$src" -maxdepth 1 -type f -name '*.md' -print0)
}

migrate_source_dir "$WIKI/concepts"
migrate_source_dir "$WIKI/entities"

echo
if [[ "$COMMIT" -eq 1 ]]; then
  echo "moved=$moved skipped=$skipped (committed)"
else
  echo "moved=$moved skipped=$skipped (dry-run — pass --commit to apply)"
fi