#!/usr/bin/env bash
# gstack-relink — re-create skill symlinks based on skill_prefix config
#
# Usage:
#   gstack-relink
#
# Env overrides (for testing):
#   GSTACK_STATE_DIR   — override ~/.gstack state directory
#   GSTACK_INSTALL_DIR — override gstack install directory
#   GSTACK_SKILLS_DIR  — override target skills directory
set -euo pipefail

SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
GSTACK_CONFIG="${SCRIPT_DIR}/gstack-config"

# Detect install dir
INSTALL_DIR="${GSTACK_INSTALL_DIR:-}"
if [ -z "$INSTALL_DIR" ]; then
  if [ -d "$HOME/.claude/skills/gstack" ]; then
    INSTALL_DIR="$HOME/.claude/skills/gstack"
  elif [ -d "${SCRIPT_DIR}/.." ] && [ -f "${SCRIPT_DIR}/../setup" ]; then
    INSTALL_DIR="$(cd "${SCRIPT_DIR}/.." && pwd)"
  fi
fi

if [ -z "$INSTALL_DIR" ] || [ ! -d "$INSTALL_DIR" ]; then
  echo "Error: gstack install directory not found." >&2
  echo "Run: cd ~/.claude/skills/gstack && ./setup" >&2
  exit 1
fi

# Detect target skills dir
SKILLS_DIR="${GSTACK_SKILLS_DIR:-$(dirname "$INSTALL_DIR")}"
[ -d "$SKILLS_DIR" ] || mkdir -p "$SKILLS_DIR"

# Read prefix setting
PREFIX=$("$GSTACK_CONFIG" get skill_prefix 2>/dev/null || echo "false")

# #2569: rendered :user variants (brain-aware blocks) live in an UNTRACKED
# out-dir instead of the tracked install checkout. When a render exists for a
# skill, relink serves it — otherwise a config change would silently flip
# every skill back to the canonical (blockless) source.
RENDER_DIR="${GSTACK_USER_RENDER_DIR:-${GSTACK_HOME:-$HOME/.gstack}/render/claude}"

# ─── Ownership gate ───────────────────────────────────────────────────────────
# relink runs on every ./setup and used to `rm -rf` any same-name entry with a
# symlinked SKILL.md and `ln -snf` over any existing SKILL.md — so a user's own
# skill that happened to share a name (a personal `qa`, a fork under another
# path) was deleted or had its SKILL.md replaced by a symlink into gstack
# (#2119; Linux replaces a real file with `ln -snf`, macOS refuses by accident).
# setup (link_claude_skill_dirs, cleanup_old_claude_symlinks,
# cleanup_prefixed_claude_symlinks) applies the same rule; keep the two files
# in sync until the shared helper filed in TODOS.md lands. gstack-uninstall
# has its own stricter inventory+banner gate.
#
# Proof comes in two strengths. STRONG (a symlink resolving into gstack, or the
# .gstack-owned marker) means we created the entry: it may be deleted whole or
# refreshed in place. WEAK (byte-identity with our source, or gen-skill-docs'
# two-line banner on a real file) proves only that the SKILL.md came from us:
# it authorizes touching that one file, never deleting the directory, and a
# differing file is moved to ${GSTACK_HOME:-~/.gstack}/backups/skills/<ts>/
# before we link over it (a user who started their own skill from a gstack
# SKILL.md looks exactly like a pre-marker legacy copy).
#
# An entry is OURS when:
#   - it is a symlink resolving into $INSTALL_DIR or $RENDER_DIR (as written or
#     as realpath), or into any path with a `gstack` segment — the convention
#     setup and gstack-uninstall use, so a sibling worktree's entries and a
#     moved checkout's dangling links still count as ours, or
#   - it is a real dir whose SKILL.md is such a symlink, or
#   - it is a real dir with a real-file SKILL.md proven by the .gstack-owned
#     marker (Windows copy installs), byte-identity with our source, or
#     gen-skill-docs' generated header (legacy copies made before the marker).
# Anything else — a foreign symlink, a real dir with a hand-written SKILL.md,
# or an entry whose readlink fails — is FOREIGN: never deleted, never linked
# over, reported on stderr.
# The install/render roots as written AND as resolved: a standalone relink
# detects INSTALL_DIR as ~/.claude/skills/gstack, which may itself be a symlink
# to a checkout, while setup linked entries against the checkout's real path.
# Both spellings are ours. (Roots stay quoted inside the case patterns, so a
# glob character or space in a path is matched literally.)
_INSTALL_REAL="$(cd "$INSTALL_DIR" 2>/dev/null && pwd -P || printf '%s' "$INSTALL_DIR")"
_RENDER_REAL="$(cd "$RENDER_DIR" 2>/dev/null && pwd -P || printf '%s' "$RENDER_DIR")"
_target_is_ours() {
  # $1 = an ABSOLUTE path a symlink resolves to; ours when it lives under one
  # of our roots. "$ROOT"/* requires the separator, so /home/u/gstack2/x never
  # matches a /home/u/gstack root.
  local root
  case "$1" in
    "$INSTALL_DIR"/*|"$RENDER_DIR"/*|"$_INSTALL_REAL"/*|"$_RENDER_REAL"/*) return 0 ;;
    gstack/*|*/gstack/*|*/.gstack/render/claude/*) return 0 ;;
  esac
  # A checkout named without a `gstack` segment (git worktree add
  # ../gstack-<branch>): the target's skill root is a gstack tree if it
  # carries setup + VERSION + bin/gstack-relink (a hand-written skill repo with
  # a VERSION file does not). Same rule as setup's _gstack_target_is_ours.
  root="${1%/*/SKILL.md}"
  if [ "$root" != "$1" ] && [ -f "$root/VERSION" ] && [ -f "$root/setup" ] && [ -f "$root/bin/gstack-relink" ]; then return 0; fi
  return 1
}

# readlink of a RELATIVE symlink (older installs wrote `gstack/qa/SKILL.md`)
# is relative to the link's own directory, not to $PWD. Anchor it there, then
# canonicalize the DIRECTORY part (pwd -P) so `..` segments and symlinked
# path components (a `gstack` alias dir, a symlinked install) compare against
# the real roots. The basename is kept verbatim: canonicalizing it would follow
# the final link and turn every dangling target into "not ours".
_link_target_abs() {
  local link="$1" dest d b d_real
  dest="$(readlink "$link" 2>/dev/null || true)"
  [ -n "$dest" ] || return 1
  case "$dest" in
    /*) ;;
    *)  dest="${link%/*}/$dest" ;;
  esac
  d="${dest%/*}"; b="${dest##*/}"
  if d_real="$(cd "$d" 2>/dev/null && pwd -P)"; then
    printf '%s\n' "$d_real/$b"
  else
    printf '%s\n' "$dest"
  fi
}

# _entry_owned_strongly ENTRY — we created this entry: a symlink resolving
# into gstack, or a real dir carrying the .gstack-owned marker or a SKILL.md
# symlink into gstack.
_entry_owned_strongly() {
  local entry="$1" dest
  if [ -L "$entry" ]; then
    dest="$(_link_target_abs "$entry")" || return 1
    _target_is_ours "$dest"
    return $?
  fi
  [ -d "$entry" ] || return 1
  [ -f "$entry/.gstack-owned" ] && return 0
  if [ -L "$entry/SKILL.md" ]; then
    dest="$(_link_target_abs "$entry/SKILL.md")" || return 1
    _target_is_ours "$dest"
    return $?
  fi
  return 1
}

# _entry_is_ours ENTRY SKILL — strong proof, or WEAK proof on a real-file
# SKILL.md (SKILL names the gstack skill this entry would serve, so the copy
# can be compared against our own source).
_entry_is_ours() {
  local entry="$1" skill="${2:-}" src
  _entry_owned_strongly "$entry" && return 0
  # A symlink that did not resolve into gstack is someone else's; never follow
  # it into the "unclaimed directory" rule below.
  [ -L "$entry" ] && return 1
  if [ -d "$entry" ] && [ ! -L "$entry/SKILL.md" ]; then
    # No SKILL.md at all: an UNCLAIMED directory (a weak cleanup left the
    # user's other files behind, or the dir was never a skill). Adding our
    # SKILL.md overwrites nothing, so the link pass may proceed; the cleanup
    # pass has nothing of ours to remove (see _cleanup_skill_entry).
    [ -e "$entry/SKILL.md" ] || return 0
    if [ -f "$entry/SKILL.md" ]; then
      for src in "$RENDER_DIR/$skill/SKILL.md" "$INSTALL_DIR/$skill/SKILL.md"; do
        [ -n "$skill" ] && [ -f "$src" ] && cmp -s "$entry/SKILL.md" "$src" && return 0
      done
      # Pre-marker legacy copy: gen-skill-docs' full two-line banner near the
      # top (same rule as setup's _gstack_generated_header), not a one-line
      # substring another generator could emit. A gstack fork rendering the
      # same banner is the accepted, filed residual.
      case "$(head -c 8192 "$entry/SKILL.md" 2>/dev/null)" in
        *'<!-- AUTO-GENERATED from '*'<!-- Regenerate: bun run gen:skill-docs -->'*) return 0 ;;
      esac
    fi
    return 1
  fi
  return 1
}

FOREIGN_SKIPPED=()
_report_foreign() {
  # Same wording and bare name as setup's own line, so setup can dedupe when it
  # forwards relink's output.
  echo "  skipped ${1##*/}: existing entry is not gstack-managed (foreign skill with the same name) — left untouched" >&2
  FOREIGN_SKIPPED+=("${1##*/}")
}

# Weakly-proven real files we would otherwise overwrite go here, one summary
# line at the end. mv, not cp: the link that follows needs the path free.
BACKUP_ROOT="${GSTACK_HOME:-$HOME/.gstack}/backups/skills/$(date +%Y%m%dT%H%M%S)"
BACKED_UP=()
_backup_skill_md() {
  # Non-zero when the file could NOT be moved: the caller leaves the entry alone.
  local file="$1" name="$2"
  mkdir -p "$BACKUP_ROOT/$name" 2>/dev/null || return 1
  mv -f "$file" "$BACKUP_ROOT/$name/SKILL.md" 2>/dev/null || return 1
  BACKED_UP+=("$name")
  return 0
}

# Helper: remove an OLD skill entry from the opposite prefix mode. Only entries
# we can prove are ours are removed; anything else is reported and kept.
_cleanup_skill_entry() {
  local entry="$1" skill="${2:-}" e dest src
  [ -e "$entry" ] || [ -L "$entry" ] || return 0
  # Unclaimed dir (no SKILL.md, no marker): nothing of ours to clean.
  if [ -d "$entry" ] && [ ! -L "$entry" ] && [ ! -e "$entry/SKILL.md" ] && [ ! -L "$entry/SKILL.md" ] && [ ! -f "$entry/.gstack-owned" ]; then
    return 0
  fi
  if ! _entry_is_ours "$entry" "$skill"; then
    _report_foreign "$entry"
    return 0
  fi
  if [ -L "$entry" ]; then
    rm -f "$entry"
  elif [ -d "$entry" ]; then
    # Whole-directory removal needs proof that nothing of the user's is inside:
    # the marker (we created the dir) or a directory holding nothing but links.
    if [ -f "$entry/.gstack-owned" ] || { [ -L "$entry/SKILL.md" ] && _dir_only_links "$entry"; }; then
      rm -rf "$entry"
    else
      # Otherwise only what is ours goes: the SKILL.md, the marker, and our
      # runtime-asset links. The user's files stay, and so does the directory
      # if it is not empty afterwards. A real SKILL.md that differs from our
      # source (raw, or with its name: rewritten to the entry name) is a
      # customized file: moved to the backup root, never deleted.
      if [ -f "$entry/SKILL.md" ] && [ ! -L "$entry/SKILL.md" ] && [ -n "$skill" ]; then
        src="$INSTALL_DIR/$skill/SKILL.md"; [ -f "$RENDER_DIR/$skill/SKILL.md" ] && src="$RENDER_DIR/$skill/SKILL.md"
        if [ -f "$src" ] && ! cmp -s "$entry/SKILL.md" "$src" \
           && ! sed "1,/^---\$/ s/^name:[[:space:]].*/name: ${entry##*/}/" "$src" | cmp -s - "$entry/SKILL.md"; then
          if ! _backup_skill_md "$entry/SKILL.md" "${entry##*/}"; then
            echo "  kept ${entry##*/}/SKILL.md: could not back up the customized file — left untouched" >&2
            return 0
          fi
        fi
      fi
      rm -f "$entry/SKILL.md" "$entry/.gstack-owned"
      for e in "$entry"/* "$entry"/.[!.]* "$entry"/..?*; do
        [ -L "$e" ] || continue
        dest="$(_link_target_abs "$e")" || continue
        if _target_is_ours "$dest"; then rm -f "$e"; fi
      done
      rmdir "$entry" 2>/dev/null || echo "  cleaned ${entry##*/}/SKILL.md (other files in that directory were left in place)"
    fi
  fi
}
# _dir_only_links DIR — deleting DIR whole loses no real data: every entry is
# a symlink or our marker.
_dir_only_links() {
  # Every entry must be a symlink resolving into gstack, or our marker: a
  # user's own link (notes.md -> ~/notes) makes the directory mixed.
  local d="$1" e dest
  for e in "$d"/* "$d"/.[!.]* "$d"/..?*; do
    { [ -e "$e" ] || [ -L "$e" ]; } || continue
    [ "${e##*/}" = ".gstack-owned" ] && continue
    [ -L "$e" ] || return 1
    dest="$(_link_target_abs "$e")" || return 1
    _target_is_ours "$dest" || return 1
  done
  return 0
}

_link_root_skill_alias() {
  local target="$SKILLS_DIR/_gstack-command"

  [ -f "$INSTALL_DIR/SKILL.md" ] || return 0
  # Same ownership gate as every other entry (#2119): a user's own
  # `_gstack-command` skill is reported and left alone, never overwritten.
  if { [ -e "$target" ] || [ -L "$target" ]; } && ! _entry_is_ours "$target" ""; then
    _report_foreign "$target"
    return 0
  fi
  local pre=0
  if [ -e "$target" ] || [ -L "$target" ]; then pre=1; fi
  [ -L "$target" ] && rm -f "$target"
  mkdir -p "$target"
  # Copy-then-rewrite, never a symlink (#2511): a symlinked alias re-serves
  # the canonical `name: gstack`, Claude Code sees a duplicate skill name,
  # and drops the ENTIRE personal-skills set. sed reads the source and writes
  # a fresh copy — remove any prior symlink first so the redirect can never
  # write through it into the generated source.
  rm -f "$target/SKILL.md"
  sed "1,/^---\$/ s/^name:[[:space:]].*/name: _gstack-command/" "$INSTALL_DIR/SKILL.md" > "$target/SKILL.md"
  # The rewritten copy is a real file on every platform: the marker, not the
  # banner, is what proves it ours on the next run — written only for a
  # directory we created (or already marked), never one we merely wrote into.
  if [ "$pre" -eq 0 ] || [ -f "$target/.gstack-owned" ]; then
    printf '%s\n' "$_INSTALL_REAL" > "$target/.gstack-owned" 2>/dev/null || true
  fi
}

_link_root_skill_alias

# Discover skills (directories with SKILL.md, excluding meta dirs)
SKILL_COUNT=0
for skill_dir in "$INSTALL_DIR"/*/; do
  [ -d "$skill_dir" ] || continue
  # Skip symlinked skill dirs (connect-chrome → open-gstack-browser): linking
  # one under the symlink's basename would duplicate the canonical frontmatter
  # name and collide in Claude Code's skill registry (#2201). setup owns the
  # rewritten-copy alias for those.
  [ -L "${skill_dir%/}" ] && continue
  skill=$(basename "$skill_dir")
  # Skip non-skill directories
  case "$skill" in bin|browse|design|docs|extension|lib|node_modules|scripts|test|.git|.github) continue ;; esac
  [ -f "$skill_dir/SKILL.md" ] || continue

  if [ "$PREFIX" = "true" ]; then
    # Don't double-prefix directories already named gstack-*
    case "$skill" in
      gstack-*) link_name="$skill" ;;
      *)        link_name="gstack-$skill" ;;
    esac
    # Remove old flat entry if it exists (and isn't the same as the new link)
    [ "$link_name" != "$skill" ] && _cleanup_skill_entry "$SKILLS_DIR/$skill" "$skill"
  else
    link_name="$skill"
    # Don't remove gstack-* dirs that are their real name (e.g., gstack-upgrade)
    case "$skill" in
      gstack-*) ;; # Already the real name, no old prefixed link to clean
      *)        _cleanup_skill_entry "$SKILLS_DIR/gstack-$skill" "$skill" ;;
    esac
  fi
  target="$SKILLS_DIR/$link_name"
  # A destination that already exists and is NOT ours is a foreign skill that
  # shares our name. Never `ln -snf` over its SKILL.md (on Linux that replaces
  # a real file with a symlink into gstack) and never mkdir into it — skip
  # loudly and leave registration of that one name to the user.
  if { [ -e "$target" ] || [ -L "$target" ]; } && ! _entry_is_ours "$target" "$skill"; then
    _report_foreign "$target"
    continue
  fi
  # Remember whether WE are creating this directory: only then may the marker
  # below make it deletable whole. A directory we merely link into (unclaimed,
  # or a legacy install) never gets one — legacy all-links dirs are removed by
  # the only-links rule instead.
  _pre_exists=0
  if [ -e "$target" ] || [ -L "$target" ]; then _pre_exists=1; fi
  # Upgrade old directory symlinks to real directories
  [ -L "$target" ] && rm -f "$target"
  # Create real directory with symlinked SKILL.md (absolute path)
  mkdir -p "$target"
  skill_md_src="$INSTALL_DIR/$skill/SKILL.md"
  [ -f "$RENDER_DIR/$skill/SKILL.md" ] && skill_md_src="$RENDER_DIR/$skill/SKILL.md"
  # A real-file SKILL.md we can only WEAKLY prove ours and whose content
  # differs from what we are about to serve is moved aside, not overwritten.
  if [ -f "$target/SKILL.md" ] && [ ! -L "$target/SKILL.md" ] && ! _entry_owned_strongly "$target" \
     && ! cmp -s "$target/SKILL.md" "$skill_md_src"; then
    if ! _backup_skill_md "$target/SKILL.md" "$link_name"; then
      echo "  skipped $link_name: could not back up its customized SKILL.md — left untouched" >&2
      FOREIGN_SKIPPED+=("$link_name")
      continue
    fi
  fi
  ln -snf "$skill_md_src" "$target/SKILL.md"
  # Provenance marker on every platform (path-independent proof; on Windows
  # without Developer Mode `ln -snf` degrades to a copy and this is the only
  # proof), but only for a directory we created or already owned.
  if [ "$_pre_exists" -eq 0 ] || [ -f "$target/.gstack-owned" ]; then
    printf '%s\n' "$_INSTALL_REAL" > "$target/.gstack-owned" 2>/dev/null || true
  fi
  SKILL_COUNT=$((SKILL_COUNT + 1))
done

# Patch SKILL.md name: fields to match prefix setting. When a gbrain render
# is active the loop above links SKILL.md from RENDER_DIR — the file the host
# actually serves — so patch THAT tree too or skill_prefix=true is a no-op
# for every brain-aware skill (#2738). gstack-patch-names takes an arbitrary
# root, skips already-prefixed names (idempotent), and the render dir is
# user-owned and untracked, so patching it never dirties a checkout.
"$INSTALL_DIR/bin/gstack-patch-names" "$INSTALL_DIR" "$PREFIX"
[ -d "$RENDER_DIR" ] && "$INSTALL_DIR/bin/gstack-patch-names" "$RENDER_DIR" "$PREFIX"

if [ "$PREFIX" = "true" ]; then
  echo "Relinked $SKILL_COUNT skills as gstack-*"
else
  echo "Relinked $SKILL_COUNT skills as flat names"
fi
if [ ${#BACKED_UP[@]} -gt 0 ]; then
  echo "Moved ${#BACKED_UP[@]} pre-existing SKILL.md file(s) to $BACKUP_ROOT before linking gstack's: ${BACKED_UP[*]}"
fi
if [ ${#FOREIGN_SKIPPED[@]} -gt 0 ]; then
  echo "Skipped ${#FOREIGN_SKIPPED[@]} foreign entr$( [ ${#FOREIGN_SKIPPED[@]} -eq 1 ] && echo y || echo ies) (not gstack-managed, left untouched): ${FOREIGN_SKIPPED[*]}"
fi