#!/bin/sh
# generate-index — rebuild SKILLS_INDEX.md's table from skill frontmatter.
#
# The index was hand-maintained and drifted: `dream` and `experiment-spec`
# shipped with no row at all, because their rows lived on branches that were
# squash-merged after a directory reorg (#15). A gate catches that after the
# fact; generating removes the class (#29).
#
# The curated summary and trigger live in each SKILL.md as `summary:` and
# `use_when:` rather than being derived from `description:` — description is a
# paragraph written for model selection, and truncating it produces a worse
# table than the one being replaced.
#
# Everything outside the markers is left untouched: the wiring docs, the
# relationships tree and the trigger table are prose, not data.
#
#   generate-index [root]           rewrite the table in place
#   generate-index --check [root]   exit 1 if the table is out of date

set -u

CHECK=0
if [ "${1:-}" = "--check" ]; then CHECK=1; shift; fi
ROOT=${1:-$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)}
INDEX="$ROOT/SKILLS_INDEX.md"

BEGIN='<!-- BEGIN skills-table -->'
END='<!-- END skills-table -->'

[ -f "$INDEX" ] || { echo "ERROR: missing $INDEX" >&2; exit 1; }
grep -qF "$BEGIN" "$INDEX" || { echo "ERROR: $INDEX has no $BEGIN marker" >&2; exit 1; }
grep -qF "$END" "$INDEX" || { echo "ERROR: $INDEX has no $END marker" >&2; exit 1; }

# field <file> <key> — a scalar frontmatter value, quotes stripped.
field() {
  sed -n "s/^$2:[[:space:]]*//p" "$1" | head -1 | sed 's/^"//; s/"$//'
}

table=$(mktemp)
fail=0

{
  printf '| Skill | Description | Use when | Surfaces |\n'
  printf '|-------|-------------|----------|----------|\n'
} > "$table"

for dir in "$ROOT"/skills/*/; do
  [ -f "$dir/SKILL.md" ] || continue
  name=$(basename "$dir")
  summary=$(field "$dir/SKILL.md" summary)
  use_when=$(field "$dir/SKILL.md" use_when)
  surfaces=$(field "$dir/SKILL.md" surfaces | tr -d '[]')

  if [ -z "$summary" ] || [ -z "$use_when" ]; then
    echo "ERROR: skills/$name has no 'summary:'/'use_when:' — the index table is generated from them" >&2
    fail=1
    continue
  fi
  printf '| `%s` | %s | %s | %s |\n' "$name" "$summary" "$use_when" "$surfaces" >> "$table"
done

if [ "$fail" -ne 0 ]; then
  rm -f "$table"
  exit 1
fi

out=$(mktemp)
awk -v begin="$BEGIN" -v end="$END" -v tablefile="$table" '
  $0 == begin { print; while ((getline line < tablefile) > 0) print line; skip = 1; next }
  $0 == end   { print; skip = 0; next }
  !skip       { print }
' "$INDEX" > "$out"
rm -f "$table"

if [ "$CHECK" -eq 1 ]; then
  if cmp -s "$out" "$INDEX"; then
    rm -f "$out"
    exit 0
  fi
  rm -f "$out"
  echo "ERROR: SKILLS_INDEX.md is out of date — run 'task index' and commit the result" >&2
  exit 1
fi

mv "$out" "$INDEX"