#!/usr/bin/env bash
# scan.sh — enumerate skill files, extract frontmatter and UTC mtime
# Usage: scan.sh [CWD_SKILLS_DIR]
# Output: JSON to stdout
#
# When CWD_SKILLS_DIR is omitted, defaults to $PWD/.claude/skills so the
# script always picks up project-level skills without relying on the caller.
#
# Environment:
#   SKILL_STOCKTAKE_GLOBAL_DIR   Override ~/.claude/skills (for testing only;
#                                do not set in production — intended for bats tests)
#   SKILL_STOCKTAKE_PROJECT_DIR  Override project dir detection (for testing only)

set -euo pipefail

sort_nul_file() {
  local input_file="$1"
  local sorted_file="${input_file}.sorted"
  node -e '
    const fs = require("fs");
    const input = fs.readFileSync(0);
    const records = [];
    let start = 0;
    for (let index = 0; index < input.length; index += 1) {
      if (input[index] === 0) {
        records.push(input.subarray(start, index + 1));
        start = index + 1;
      }
    }
    if (start < input.length) records.push(input.subarray(start));
    records.sort(Buffer.compare);
    process.stdout.write(Buffer.concat(records));
  ' <"$input_file" >"$sorted_file"
  mv "$sorted_file" "$input_file"
}

GLOBAL_DIR="${SKILL_STOCKTAKE_GLOBAL_DIR:-$HOME/.claude/skills}"
CWD_SKILLS_DIR="${SKILL_STOCKTAKE_PROJECT_DIR:-${1:-$PWD/.claude/skills}}"
# Path to JSONL file containing tool-use observations (optional; used for usage frequency counts).
# Override via SKILL_STOCKTAKE_OBSERVATIONS env var if your setup uses a different path.
OBSERVATIONS="${SKILL_STOCKTAKE_OBSERVATIONS:-$HOME/.claude/observations.jsonl}"

# Validate CWD_SKILLS_DIR looks like a .claude/skills path (defense-in-depth).
# Only warn when the path exists — a nonexistent path poses no traversal risk.
if [[ -n "$CWD_SKILLS_DIR" && -d "$CWD_SKILLS_DIR" && "$CWD_SKILLS_DIR" != */.claude/skills* ]]; then
  echo "Warning: CWD_SKILLS_DIR does not look like a .claude/skills path: $CWD_SKILLS_DIR" >&2
fi

# Extract a frontmatter field (handles both quoted and unquoted single-line values).
# Does NOT support multi-line YAML blocks (| or >) or nested YAML keys.
extract_field() {
  local file="$1" field="$2"
  awk -v f="$field" '
    BEGIN { fm=0 }
    /^---$/ { fm++; next }
    fm==1 {
      n = length(f) + 2
      if (substr($0, 1, n) == f ": ") {
        val = substr($0, n+1)
        gsub(/^"/, "", val)
        gsub(/"$/, "", val)
        print val
        exit
      }
    }
    fm>=2 { exit }
  ' "$file"
}

# Get UTC timestamp N days ago (supports both macOS and GNU date)
date_ago() {
  local n="$1"
  date -u -v-"${n}d" +%Y-%m-%dT%H:%M:%SZ 2>/dev/null ||
  date -u -d "${n} days ago" +%Y-%m-%dT%H:%M:%SZ
}

# Count observations matching a file path since a cutoff timestamp
count_obs() {
  local file="$1" cutoff="$2"
  if [[ ! -f "$OBSERVATIONS" ]]; then
    echo 0
    return
  fi
  jq -r --arg p "$file" --arg c "$cutoff" \
    'select(.tool=="Read" and .path==$p and .timestamp>=$c) | 1' \
    "$OBSERVATIONS" 2>/dev/null | wc -l | tr -d ' '
}

# Scan a directory and produce a JSON array of skill objects
scan_dir_to_json() {
  local dir="$1"
  local c7 c30
  c7=$(date_ago 7)
  c30=$(date_ago 30)

  local tmpdir
  tmpdir=$(mktemp -d)
  # Use a function to avoid embedding $tmpdir in a quoted string (prevents injection
  # if TMPDIR were crafted to contain shell metacharacters).
  local _scan_tmpdir="$tmpdir"
  _scan_cleanup() { rm -rf "$_scan_tmpdir"; }
  trap _scan_cleanup RETURN

  # Pre-aggregate observation counts in two passes (one per window) instead of
  # calling jq per-file — reduces from O(n*m) to O(n+m) jq invocations.
  local obs_7d_counts obs_30d_counts
  obs_7d_counts=""
  obs_30d_counts=""
  if [[ -f "$OBSERVATIONS" ]]; then
    obs_7d_counts=$(jq -r --arg c "$c7" \
      'select(.tool=="Read" and .timestamp>=$c) | .path' \
      "$OBSERVATIONS" 2>/dev/null | sort | uniq -c)
    obs_30d_counts=$(jq -r --arg c "$c30" \
      'select(.tool=="Read" and .timestamp>=$c) | .path' \
      "$OBSERVATIONS" 2>/dev/null | sort | uniq -c)
  fi

  local i=0
  local find_out="$tmpdir/.find-stdout"
  local find_err="$tmpdir/.find-stderr"
  # Capture find's exit status and stderr instead of discarding them: with -L,
  # a broken symlink or unreadable directory makes find skip that entry AND
  # exit non-zero, which would otherwise silently under-count skills.
  # NUL-delimited (-print0 / sort_nul_file / read -d '') so a path containing a
  # literal newline can't desync record boundaries — paths here are untrusted.
  if ! find -L "$dir" -name "SKILL.md" -type f -print0 >"$find_out" 2>"$find_err"; then
    echo "Warning: find encountered errors while scanning $dir (broken symlinks or permission issues may cause skills to be missed):" >&2
    cat "$find_err" >&2
  fi
  sort_nul_file "$find_out"

  while IFS= read -r -d '' file; do
    local name desc mtime u7 u30 dp
    name=$(extract_field "$file" "name")
    desc=$(extract_field "$file" "description")
    mtime=$(date -u -r "$file" +%Y-%m-%dT%H:%M:%SZ)
    if [[ "$file" == *[[:space:]]* ]]; then
      # The aggregated fast path is line-delimited. Preserve unusual paths by
      # falling back to the structured JSON matcher for this record.
      u7=$(count_obs "$file" "$c7")
      u30=$(count_obs "$file" "$c30")
    else
      # Use awk exact field match to avoid substring false-positives from grep -F.
      # uniq -c output format: "   N /path/to/file" — path is always field 2.
      u7=$(echo "$obs_7d_counts" | awk -v f="$file" '$2 == f {print $1}' | head -1)
      u7="${u7:-0}"
      u30=$(echo "$obs_30d_counts" | awk -v f="$file" '$2 == f {print $1}' | head -1)
      u30="${u30:-0}"
    fi
    dp="${file/#$HOME/~}"

    jq -n \
      --arg path "$dp" \
      --arg name "$name" \
      --arg description "$desc" \
      --arg mtime "$mtime" \
      --argjson use_7d "$u7" \
      --argjson use_30d "$u30" \
      '{path:$path,name:$name,description:$description,use_7d:$use_7d,use_30d:$use_30d,mtime:$mtime}' \
      > "$tmpdir/$i.json"
    i=$((i+1))
  done < "$find_out"

  if [[ $i -eq 0 ]]; then
    echo "[]"
  else
    jq -s '.' "$tmpdir"/*.json
  fi
}

# --- Main ---

global_found="false"
global_count=0
global_skills="[]"

if [[ -d "$GLOBAL_DIR" ]]; then
  global_found="true"
  global_skills=$(scan_dir_to_json "$GLOBAL_DIR")
  global_count=$(echo "$global_skills" | jq 'length')
fi

project_found="false"
project_path=""
project_count=0
project_skills="[]"

if [[ -n "$CWD_SKILLS_DIR" && -d "$CWD_SKILLS_DIR" ]]; then
  project_found="true"
  project_path="$CWD_SKILLS_DIR"
  project_skills=$(scan_dir_to_json "$CWD_SKILLS_DIR")
  project_count=$(echo "$project_skills" | jq 'length')
fi

# Merge global + project skills into one array
all_skills=$(jq -s 'add' <(echo "$global_skills") <(echo "$project_skills"))

jq -n \
  --arg global_found "$global_found" \
  --argjson global_count "$global_count" \
  --arg project_found "$project_found" \
  --arg project_path "$project_path" \
  --argjson project_count "$project_count" \
  --argjson skills "$all_skills" \
  '{
    scan_summary: {
      global: { found: ($global_found == "true"), count: $global_count },
      project: { found: ($project_found == "true"), path: $project_path, count: $project_count }
    },
    skills: $skills
  }'