#!/usr/bin/env bash
# commit_msg.sh — génère un message de commit depuis les changements en cours
# Fonctionne avec git (fichiers stagés) et jj (working copy).
#
# Usage : bash .claude/hooks/commit_msg.sh

set -euo pipefail

log()  { printf '\033[1;34m==>\033[0m %s\n' "$*" >&2; }
info() { printf '    \033[0;37m%s\033[0m\n' "$*" >&2; }
ok()   { printf '    \033[0;32m✓\033[0m %s\n' "$*" >&2; }

# --- Détection du VCS ---

_detect_vcs() {
    if jj root &>/dev/null; then
        echo "jj"
    elif git rev-parse --git-dir &>/dev/null; then
        echo "git"
    else
        echo "none"
    fi
}

# --- Fichiers modifiés ---

_changed_files() {
    case "$VCS" in
        jj)  jj diff --name-only ;;
        git) git diff --staged --name-only ;;
    esac
}

# --- Diff lisible par fichier ---

_readable_diff() {
    local file="$1"
    local raw_diff

    case "$VCS" in
        jj)  raw_diff=$(jj diff -- "$file") ;;
        git) raw_diff=$(git diff --staged -- "$file") ;;
    esac

    [[ -z "$raw_diff" ]] && return 0

    local max_len
    max_len=$(grep '^[+-]' <<< "$raw_diff" 2>/dev/null \
        | awk '{ if (length > m) m = length } END { print m+0 }')

    if (( max_len <= 500 )); then
        printf '%s' "$raw_diff"
        return
    fi

    # Pretty-print pour les formats pathologiques (JSON, JS minifié…)
    local ext="${file##*.}"
    local pretty_old pretty_new

    case "$ext" in
        json)
            case "$VCS" in
                jj)
                    pretty_old=$(jj file show "${file}@-" 2>/dev/null | python3 -m json.tool 2>/dev/null || true)
                    pretty_new=$(jj file show "$file"    2>/dev/null | python3 -m json.tool 2>/dev/null || true)
                    ;;
                git)
                    pretty_old=$(git show "HEAD:${file}" 2>/dev/null | python3 -m json.tool 2>/dev/null || true)
                    pretty_new=$(git show ":${file}"     2>/dev/null | python3 -m json.tool 2>/dev/null || true)
                    ;;
            esac
            ;;
        js|mjs|cjs|css|ts)
            local node_fmt='
                const chunks = [];
                process.stdin.on("data", d => chunks.push(d));
                process.stdin.on("end", () => {
                    const src = chunks.join("");
                    const out = src
                        .replace(/([{(])/g,  "$1\n  ")
                        .replace(/([;}])/g,  "\n$1\n")
                        .replace(/,\s*/g,    ",\n  ");
                    process.stdout.write(out);
                });'
            case "$VCS" in
                jj)
                    pretty_old=$(jj file show "${file}@-" 2>/dev/null | node -e "$node_fmt" 2>/dev/null || true)
                    pretty_new=$(jj file show "$file"     2>/dev/null | node -e "$node_fmt" 2>/dev/null || true)
                    ;;
                git)
                    pretty_old=$(git show "HEAD:${file}" 2>/dev/null | node -e "$node_fmt" 2>/dev/null || true)
                    pretty_new=$(git show ":${file}"     2>/dev/null | node -e "$node_fmt" 2>/dev/null || true)
                    ;;
            esac
            ;;
        *)
            case "$VCS" in
                jj)
                    pretty_old=$(jj file show "${file}@-" 2>/dev/null | fold -s -w 120 || true)
                    pretty_new=$(jj file show "$file"     2>/dev/null | fold -s -w 120 || true)
                    ;;
                git)
                    pretty_old=$(git show "HEAD:${file}" 2>/dev/null | fold -s -w 120 || true)
                    pretty_new=$(git show ":${file}"     2>/dev/null | fold -s -w 120 || true)
                    ;;
            esac
            ;;
    esac

    if [[ -n "$pretty_old" && -n "$pretty_new" ]]; then
        diff <(printf '%s\n' "$pretty_old") <(printf '%s\n' "$pretty_new") \
            --label "a/${file}" --label "b/${file}" -u || true
    else
        printf '%s' "$raw_diff"
    fi
}

# --- Main ---

VCS=$(_detect_vcs)

if [[ "$VCS" == "none" ]]; then
    echo "ERREUR : ni git ni jj détecté dans ce répertoire." >&2
    exit 1
fi

log "VCS détecté : $VCS"

changed_files=$(_changed_files)

if [[ -z "$changed_files" ]]; then
    echo "Aucun fichier modifié." >&2
    exit 1
fi

file_count=$(wc -l <<< "$changed_files" | tr -d ' ')
log "Fichiers modifiés : $file_count"

summaries=""
n=0

while IFS= read -r file; do
    diff=$(_readable_diff "$file")
    [[ -z "$diff" ]] && continue

    n=$((n + 1))
    log "[$n/$file_count] Résumé de $file …"

    summary=$(printf '%s' "$diff" \
        | aichat "In 2-3 lines, summarise what this diff changes in the file '$file'. Be concise and technical.")

    while IFS= read -r line; do info "$line"; done <<< "$summary"

    summaries+="### $file
$summary

"
done <<< "$changed_files"

if [[ -z "$summaries" ]]; then
    echo "Aucun diff non-vide trouvé." >&2
    exit 1
fi

log "Génération du message de commit ($n fichier(s)) …"

result=$(printf '%s' "$summaries" \
    | aichat "From these per-file summaries of a diff, write a single conventional git commit message in English. First line: short imperative summary (max 72 chars). Then a blank line. Then a short paragraph with more detail if needed. Output only the commit message, nothing else.")

ok "Terminé"
printf '\n' >&2

printf '%s\n' "$result"