#!/usr/bin/env bash
# install-git-hooks.sh — Idempotent installer for Red Bear OS optional git hooks.
#
# Hooks in Red Bear OS are ALWAYS opt-in (per AGENTS.md "absolutely NEVER
# DELETE, NEVER IGNORE" rule — operators explicitly choose to install them).
# This script is a convenience wrapper around the manual `cp` instructions
# documented in local/docs/HOOKS.md. It never silently clobbers an existing
# hook: if a hook file already exists and differs from the canonical copy,
# it is backed up to `<name>.bak` before the new one is written, and a
# warning is printed.
#
# Usage:
#   ./local/scripts/install-git-hooks.sh                 # install post-checkout only (default)
#   ./local/scripts/install-git-hooks.sh --all           # post-checkout + pre-push + commit-msg
#   ./local/scripts/install-git-hooks.sh --uninstall     # remove hooks installed by this script
#   ./local/scripts/install-git-hooks.sh --uninstall --all
#
# Exit codes:
#   0  success (or already-installed, or nothing to uninstall)
#   1  fatal misconfiguration (not a git repo, scripts missing, etc.)
#
# See: local/docs/HOOKS.md (hook inventory + bypass instructions),
#      local/docs/RELEASE-BUMP-WORKFLOW.md (release-bump pipeline).

set -euo pipefail

# ---------------------------------------------------------------------------
# Resolve repo root. Must be a Red Bear OS checkout (has local/scripts/).
# ---------------------------------------------------------------------------

ROOT="$(git rev-parse --show-toplevel 2>/dev/null || true)"
if [[ -z "$ROOT" ]]; then
    echo "install-git-hooks: not inside a git work tree" >&2
    exit 1
fi

SCRIPTS_DIR="$ROOT/local/scripts"
HOOKS_DIR="$(git rev-parse --git-path hooks 2>/dev/null)"
# `git rev-parse --git-path hooks` resolves correctly for linked worktrees
# and custom $GIT_DIR. Fall back to the conventional path if it fails.
if [[ -z "$HOOKS_DIR" ]]; then
    GIT_DIR="$(git rev-parse --git-dir 2>/dev/null || echo .git)"
    [[ "$GIT_DIR" = /* ]] || GIT_DIR="$ROOT/$GIT_DIR"
    HOOKS_DIR="$GIT_DIR/hooks"
fi

mkdir -p "$HOOKS_DIR"

# ---------------------------------------------------------------------------
# Parse flags.
# ---------------------------------------------------------------------------

INSTALL_ALL=0
UNINSTALL=0
for arg in "$@"; do
    case "$arg" in
        --all)        INSTALL_ALL=1 ;;
        --uninstall)  UNINSTALL=1 ;;
        -h|--help)
            sed -n '1,30p' "$0"
            exit 0
            ;;
        *)
            echo "install-git-hooks: unknown option: $arg" >&2
            echo "  usage: $0 [--all] [--uninstall]" >&2
            exit 1
            ;;
    esac
done

# ---------------------------------------------------------------------------
# Hook manifest. The default install set is intentionally minimal (only
# post-checkout) so that a bare `install-git-hooks.sh` does the least
# surprising thing. `--all` extends to the pre-push and commit-msg hooks.
# ---------------------------------------------------------------------------

# Each entry: <hook-name>;<source-script-relative-to-local/scripts>
HOOKS_DEFAULT=(
    "post-checkout;post-checkout-version-sync.sh"
)

HOOKS_EXTRA=(
    "pre-push;pre-push-checks.sh"
    "commit-msg;commit-msg"
)

# Build the active set from the flags.
ACTIVE_HOOKS=()
if [[ $UNINSTALL -eq 1 ]]; then
    # Uninstall needs to know the full set that --all would have installed,
    # so a default-install-then---all-uninstall cleans everything up.
    for entry in "${HOOKS_DEFAULT[@]}" "${HOOKS_EXTRA[@]}"; do
        ACTIVE_HOOKS+=("$entry")
    done
    if [[ $INSTALL_ALL -eq 0 ]]; then
        # Without --all, only uninstall the default set (the ones a default
        # install would have placed). Operators who used --all should pass
        # --uninstall --all.
        ACTIVE_HOOKS=("${HOOKS_DEFAULT[@]}")
    fi
else
    ACTIVE_HOOKS=("${HOOKS_DEFAULT[@]}")
    [[ $INSTALL_ALL -eq 1 ]] && ACTIVE_HOOKS+=("${HOOKS_EXTRA[@]}")
fi

# ---------------------------------------------------------------------------
# Install / uninstall loop.
# ---------------------------------------------------------------------------

install_one() {
    local hook_name="$1"
    local src_rel="$2"
    local src="$SCRIPTS_DIR/$src_rel"
    local dst="$HOOKS_DIR/$hook_name"

    if [[ ! -f "$src" ]]; then
        echo "install-git-hooks: WARN source script not found: $src_rel — skipping $hook_name" >&2
        return 0
    fi

    if [[ -e "$dst" || -L "$dst" ]]; then
        # Content-based, not path-based: a copied hook has a different path
        # than the source, so only byte comparison detects "already current".
        if cmp -s "$dst" "$src" 2>/dev/null; then
            echo "install-git-hooks: $hook_name already up to date ($dst)"
            chmod +x "$dst" 2>/dev/null || true
            return 0
        fi
        # Existing file differs — back it up before overwriting.
        local bak="${dst}.bak"
        # Rotate any pre-existing .bak so we don't destroy the first backup.
        if [[ -e "$bak" ]]; then
            local i=1
            while [[ -e "${dst}.bak.${i}" && $i -le 100 ]]; do i=$((i+1)); done
            if [[ $i -gt 100 ]]; then
                bak="${dst}.bak.$(date +%Y%m%d%H%M%S)-$$"
            else
                bak="${dst}.bak.${i}"
            fi
        fi
        echo "install-git-hooks: WARN existing $hook_name differs — backing up to $bak" >&2
        mv "$dst" "$bak"
    fi

    cp "$src" "$dst"
    chmod +x "$dst"
    echo "install-git-hooks: installed $hook_name -> $dst"
}

uninstall_one() {
    local hook_name="$1"
    local dst="$HOOKS_DIR/$hook_name"

    if [[ ! -e "$dst" && ! -L "$dst" ]]; then
        echo "install-git-hooks: $hook_name not present ($dst) — nothing to remove"
        return 0
    fi
    rm -f "$dst"
    echo "install-git-hooks: removed $hook_name ($dst)"
    # Restore the most recent backup if one exists, so uninstall is reversible.
    if [[ -e "${dst}.bak" ]]; then
        mv "${dst}.bak" "$dst"
        chmod +x "$dst" 2>/dev/null || true
        echo "install-git-hooks: restored previous $hook_name from ${dst}.bak"
    fi
}

echo "=== Red Bear OS git hook installer ==="
echo "  repo root:  $ROOT"
echo "  hooks dir:  $HOOKS_DIR"
echo "  mode:       $([[ $UNINSTALL -eq 1 ]] && echo 'uninstall' || echo 'install') ($([[ $INSTALL_ALL -eq 1 ]] && echo 'all hooks' || echo 'default: post-checkout only'))"
echo ""

if [[ $UNINSTALL -eq 1 ]]; then
    for entry in "${ACTIVE_HOOKS[@]}"; do
        hook_name="${entry%%;*}"
        uninstall_one "$hook_name"
    done
    echo ""
    echo "Uninstall complete. Remaining hooks (if any):"
    ls -1 "$HOOKS_DIR" 2>/dev/null | grep -vE '\.bak(\.[0-9]+)?$' || echo "  (none)"
    exit 0
fi

for entry in "${ACTIVE_HOOKS[@]}"; do
    hook_name="${entry%%;*}"
    src_rel="${entry##*;}"
    install_one "$hook_name" "$src_rel"
done

echo ""
echo "=== Install complete ==="
echo ""
echo "Installed hooks are OPT-IN and never auto-commit, auto-push, or block"
echo "checkouts. Bypass / configuration:"
echo "  post-checkout: REDBEAR_NO_AUTO_SYNC=1 git checkout <branch>"
echo "  pre-push:      REDBEAR_SKIP_PRE_PUSH=1 git push  (or git push --no-verify)"
echo ""
echo "Full documentation: local/docs/HOOKS.md"
echo "Release-bump runbook: local/docs/RELEASE-BUMP-WORKFLOW.md"