#!/usr/bin/env bash
#
# .githooks/pre-commit
#
# Runs clang-format and clang-tidy against staged C/C++ files before each
# commit — no Python, no pre-commit framework, just bash and (optionally)
# the clang tools themselves.
#
# Neither tool is required to have this hook installed: if a binary isn't
# on PATH, this prints a warning and skips that check instead of blocking
# the commit. Only *actual formatting/lint issues* from a tool that IS
# installed will block a commit (unless --fix resolves them, see below).
#
# Platforms:
#   - Linux / macOS: runs under the system bash (or Homebrew bash on macOS)
#     with no extra setup.
#   - Windows: runs automatically through Git for Windows' bundled Git Bash —
#     git.exe recognizes the "#!/usr/bin/env bash" line above and executes
#     hooks through it directly, so no WSL, Cygwin, or separate bash install
#     is needed. Everything this script uses (mktemp, diff, grep, printf,
#     command -v) ships with Git for Windows out of the box.
#
# One-time setup per clone (same command on every OS):
#   chmod +x .githooks/pre-commit   (no-op on Windows, harmless either way)
#   git config core.hooksPath .githooks
#
# Usage:
#   .githooks/pre-commit                # hook mode: checks staged files, blocks on issues
#   .githooks/pre-commit --all          # checks every tracked C/C++ file, ignoring staging
#   .githooks/pre-commit --fix          # applies fixes to staged files, then re-stages them
#   .githooks/pre-commit --all --fix    # applies fixes across the whole tree (flags combine)
#
# What --fix actually does:
#   clang-format -i         always safe — pure whitespace/layout, never changes behavior.
#   clang-tidy --fix        NOT always safe — some checks (e.g. identifier renames) can
#                            occasionally produce code that doesn't compile if the fix is
#                            context-sensitive. Review the diff after running --fix before
#                            you trust it blindly, especially the first few times.
#
# In staged (non --all) mode, --fix re-stages (git add) any file it modifies, so the
# fixed version — not the original — is what actually gets committed. In --all mode
# nothing is staged automatically; you review and commit the changes yourself.
set -uo pipefail

# Colors only when writing to an interactive terminal — avoids raw escape
# codes in CI logs, redirected output, or terminals that don't support ANSI.
if [ -t 1 ]; then
    RED=$'\033[0;31m'
    YELLOW=$'\033[0;33m'
    GREEN=$'\033[0;32m'
    RESET=$'\033[0m'
else
    RED=''
    YELLOW=''
    GREEN=''
    RESET=''
fi

exit_code=0

# --- Flag parsing (order-independent) ---
# --all: check every tracked file matching the patterns, ignoring staging
#        state entirely (git ls-files, not git diff --cached).
# --fix: apply fixes in place instead of just reporting them.
all_mode=0
fix_mode=0
for arg in "$@"; do
    case "$arg" in
        --all) all_mode=1 ;;
        --fix) fix_mode=1 ;;
        *)
            echo "${RED}unknown argument: $arg${RESET}"
            echo "usage: $0 [--all] [--fix]"
            exit 2
            ;;
    esac
done

# --- Collect C/C++ files (added/copied/modified, or all tracked in --all mode) ---
# ':!vendor/*' excludes third-party code vendored under vendor/ (see
# cmake/Dependencies.cmake in the parent project) -- it isn't this
# project's code, so it isn't held to this style guide. Not part of the
# toolkit as shipped; added for this project's vendor/ convention.
files=()
if [ "$all_mode" -eq 1 ]; then
    echo "mode: --all (checking every tracked C/C++ file via 'git ls-files')"
    while IFS= read -r line; do
        [ -n "$line" ] && files+=("$line")
    done < <(git ls-files -- \
        '*.c' '*.h' '*.cpp' '*.hpp' '*.cc' '*.cxx' '*.tpp' ':!vendor/*')
else
    echo "mode: staged (checking files via 'git diff --cached')"
    while IFS= read -r line; do
        [ -n "$line" ] && files+=("$line")
    done < <(git diff --cached --name-only --diff-filter=ACM -- \
        '*.c' '*.h' '*.cpp' '*.hpp' '*.cc' '*.cxx' '*.tpp' ':!vendor/*')
fi

if [ "$fix_mode" -eq 1 ]; then
    echo "fix: enabled (issues will be corrected in place, not just reported)"
fi

if [ ${#files[@]} -eq 0 ]; then
    echo "${YELLOW}no matching C/C++ files found — nothing to check.${RESET}"
    exit 0
fi

echo "found ${#files[@]} file(s) to check:"
printf '  %s\n' "${files[@]}"

# --- clang-format: check (or fix) formatting ---
if command -v clang-format >/dev/null 2>&1; then
    if [ "$fix_mode" -eq 1 ]; then
        echo "running clang-format --fix (in-place, $(command -v clang-format))..."
        fixed=()
        for f in "${files[@]}"; do
            [ -f "$f" ] || continue
            if ! diff -q <(clang-format "$f") "$f" >/dev/null 2>&1; then
                clang-format -i "$f"
                fixed+=("$f")
            fi
        done
        if [ ${#fixed[@]} -gt 0 ]; then
            echo "${GREEN}clang-format: reformatted ${#fixed[@]} file(s):${RESET}"
            printf '  %s\n' "${fixed[@]}"
            if [ "$all_mode" -eq 0 ]; then
                git add -- "${fixed[@]}"
                echo "re-staged the fixed file(s) so they're included in this commit."
            fi
        fi
    else
        echo "running clang-format check ($(command -v clang-format))..."
        unformatted=()
        for f in "${files[@]}"; do
            [ -f "$f" ] || continue
            if ! diff -q <(clang-format "$f") "$f" >/dev/null 2>&1; then
                unformatted+=("$f")
            fi
        done
        if [ ${#unformatted[@]} -gt 0 ]; then
            echo "${RED}clang-format: these files aren't formatted:${RESET}"
            printf '  %s\n' "${unformatted[@]}"
            echo "Fix with: clang-format -i ${unformatted[*]}"
            echo "(or rerun this hook with --fix to apply automatically)"
            exit_code=1
        fi
    fi
else
    echo "${YELLOW}warning: clang-format not found on PATH — skipping format check.${RESET}"
fi

# --- clang-tidy: static analysis (or fix), needs a compile database ---
if command -v clang-tidy >/dev/null 2>&1; then
    if [ ! -f compile_commands.json ]; then
        echo "${YELLOW}warning: compile_commands.json not found — skipping clang-tidy.${RESET}"
        echo "${YELLOW}Generate one with: cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ...${RESET}"
    else
        tidy_output=$(mktemp)
        tidy_had_issues=0
        if [ "$fix_mode" -eq 1 ]; then
            echo "running clang-tidy --fix (in-place, $(command -v clang-tidy))..."
            echo "${YELLOW}note: some clang-tidy fixes are context-sensitive and can occasionally${RESET}"
            echo "${YELLOW}produce code that doesn't compile — review the diff before trusting it.${RESET}"
            for f in "${files[@]}"; do
                [ -f "$f" ] || continue
                if ! clang-tidy --quiet --fix --fix-errors -p . "$f" >>"$tidy_output" 2>&1; then
                    tidy_had_issues=1
                fi
            done
            if [ "$all_mode" -eq 0 ]; then
                changed=()
                while IFS= read -r line; do
                    [ -n "$line" ] && changed+=("$line")
                done < <(git diff --name-only -- "${files[@]}")
                if [ ${#changed[@]} -gt 0 ]; then
                    git add -- "${changed[@]}"
                    echo "${GREEN}clang-tidy: modified and re-staged ${#changed[@]} file(s):${RESET}"
                    printf '  %s\n' "${changed[@]}"
                fi
            fi
        else
            echo "running clang-tidy check ($(command -v clang-tidy))..."
            for f in "${files[@]}"; do
                [ -f "$f" ] || continue
                if ! clang-tidy --quiet "$f" >>"$tidy_output" 2>&1; then
                    tidy_had_issues=1
                fi
            done
        fi

        if grep -q "warning:\|error:" "$tidy_output" 2>/dev/null; then
            if [ "$fix_mode" -eq 1 ]; then
                echo "${YELLOW}clang-tidy: issues remaining after fix attempt (not all checks can auto-fix):${RESET}"
            else
                echo "${RED}clang-tidy found issues:${RESET}"
                echo "(rerun this hook with --fix to auto-correct what clang-tidy can fix)"
            fi
            cat "$tidy_output"
            exit_code=1
        elif [ "$tidy_had_issues" -eq 1 ]; then
            # Non-zero exit with no warning/error text usually means clang-tidy
            # itself couldn't run (e.g. missing headers) — surface it, but
            # don't block the commit on a tooling problem rather than a style one.
            echo "${YELLOW}warning: clang-tidy exited with an error unrelated to style:${RESET}"
            cat "$tidy_output"
        fi
        rm -f "$tidy_output"
    fi
else
    echo "${YELLOW}warning: clang-tidy not found on PATH — skipping static analysis.${RESET}"
fi

if [ $exit_code -eq 0 ]; then
    echo "${GREEN}pre-commit checks passed.${RESET}"
fi

exit $exit_code