#!/usr/bin/env bash
set -euo pipefail

# Usage:
#   check-history.sh <start_offset> <count> [OPTIONS]
# Example:
#   check-history.sh 2 4         # checks commits 2,3,4,5
#   check-history.sh 5 1 -v      # verbose mode
#   check-history.sh 2 28 -j4    # check 28 commits, 4 at a time

VERBOSE=0
JOBS=1

# Parse arguments
if [ $# -lt 2 ]; then
    echo "Usage: $0 <start_offset_from_head> <count> [--verbose|-v] [-j|--jobs N]"
    exit 1
fi

START_ARG="$1"
COUNT_ARG="$2"
shift 2

# Parse optional flags
while [ $# -gt 0 ]; do
    case "$1" in
        -v|--verbose)
            VERBOSE=1
            shift
            ;;
        -j|--jobs)
            if [ $# -lt 2 ]; then
                echo "Error: -j/--jobs requires a number" >&2
                exit 1
            fi
            JOBS="$2"
            if ! [[ "$JOBS" =~ ^[0-9]+$ ]] || [ "$JOBS" -lt 1 ]; then
                echo "Error: -j/--jobs must be a positive integer" >&2
                exit 1
            fi
            shift 2
            ;;
        *)
            echo "Error: Unknown option $1" >&2
            echo "Usage: $0 <start_offset_from_head> <count> [--verbose|-v] [-j|--jobs N]"
            exit 1
            ;;
    esac
done

# Debug logging helper
debug() {
    if [ "$VERBOSE" -eq 1 ]; then
        echo "[DEBUG] $*" >&2
    fi
}

# Convert user-friendly 1-indexed "Nth from HEAD" into 0-indexed offset
START_OFFSET="$(( START_ARG - 1 ))"
COUNT="$COUNT_ARG"
REPO_ROOT="$(git rev-parse --show-toplevel)"
TMP_BASE="/tmp/check-history-$$"
WORKTREES_DIR="$TMP_BASE/worktrees"
LOGS_DIR="$TMP_BASE/logs"
PNPM_STORE="$HOME/.cache/check-history/pnpm-store"

debug "REPO_ROOT: $REPO_ROOT"
debug "TMP_BASE: $TMP_BASE"
debug "PNPM_STORE: $PNPM_STORE"

mkdir -p "$WORKTREES_DIR" "$LOGS_DIR" "$PNPM_STORE"

if [ "$JOBS" -gt 1 ]; then
    echo "Checking commits from offset $START_ARG (HEAD~$START_OFFSET) for $COUNT commits with $JOBS parallel jobs…"
else
    echo "Checking commits from offset $START_ARG (HEAD~$START_OFFSET) for $COUNT commits…"
fi
echo

# Build list of commits as if by `git rebase -i HEAD~N` (HEAD=0 newest) as if by `git rebase -i HEAD~N`
# HEAD = index 0, parent = index 1, etc.
mapfile -t HEAD_TO_OLD <<EOF
$(git rev-list HEAD)
EOF

# Reverse into chronological order (oldest first)
mapfile -t ALL_COMMITS < <(printf '%s
' "${HEAD_TO_OLD[@]}" | tac)

debug "Total commits in history: ${#ALL_COMMITS[@]}"
mapfile -t ALL_COMMITS < <(printf '%s
' "${HEAD_TO_OLD[@]}" | tac)

# Convert HEAD-based offsets to chronological indexes
# HEAD~0 → last element; HEAD~1 → second-to-last
START_INDEX=$(( ${#ALL_COMMITS[@]} - 1 - START_OFFSET ))
debug "START_INDEX (in chronological array): $START_INDEX"

# Corrected: START_INDEX is the *newest* selected commit.
# The range must be: START_INDEX down to START_INDEX-(COUNT-1)
BEGIN_INDEX=$(( START_INDEX - COUNT + 1 ))
debug "BEGIN_INDEX: $BEGIN_INDEX (checking $COUNT commits)"

# True rebase-style selection: newest-first offset, then N older
# Ensure BEGIN_INDEX is valid
if (( BEGIN_INDEX < 0 )); then
    echo "Error: Range extends beyond repository history" >&2
    exit 1
fi

# Compute slice from BEGIN_INDEX to START_INDEX inclusive
COMMITS=("${ALL_COMMITS[@]:$BEGIN_INDEX:$COUNT}")
debug "Selected commits:"
for c in "${COMMITS[@]}"; do
    debug "  $c"
done
# -----------------------------
# Frontend builder
# -----------------------------
build_frontend() {
    (
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] Entering rfc-edge-frontend directory" || true
        cd rfc-edge-frontend || {
            echo "❌ Failed to cd into rfc-edge-frontend"
            return 1
        }
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] cd succeeded, PWD=$PWD" || true

        export PNPM_HOME="$PWD/.pnpm_home"
        export PNPM_STORE_PATH="$PNPM_STORE"
        export PNPM_HARD_LINKS=false

        # Copy .env file from main repo if it exists and isn't present in worktree
        if [ ! -f .env ] && [ -f "$REPO_ROOT/rfc-edge-frontend/.env" ]; then
            [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] Copying .env file from main repo" || true
            cp "$REPO_ROOT/rfc-edge-frontend/.env" .env
        elif [ -f .env ]; then
            [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] .env file already exists in worktree" || true
        else
            [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] No .env file found in main repo" || true
        fi

        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] Environment variables set:" || true
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG]   PNPM_HOME=$PNPM_HOME" || true
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG]   PNPM_STORE_PATH=$PNPM_STORE_PATH" || true

        mkdir -p "$PNPM_HOME" "$PNPM_STORE_PATH"
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] Created pnpm directories" || true

        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] Running pnpm install..." || true
        if [ "$VERBOSE" -eq 1 ]; then
            pnpm install --frozen-lockfile --prefer-offline </dev/null
        else
            pnpm install --frozen-lockfile --prefer-offline </dev/null >/dev/null 2>&1
        fi || {
            echo "❌ pnpm install failed"
            return 1
        }
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] pnpm install succeeded" || true

        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] Running pnpm build..." || true
        if [ "$VERBOSE" -eq 1 ]; then
            pnpm build </dev/null
        else
            pnpm build </dev/null >/dev/null 2>&1
        fi || {
            echo "❌ pnpm build failed"
            return 1
        }
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] pnpm build succeeded" || true

        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] Running pnpm check..." || true
        if [ "$VERBOSE" -eq 1 ]; then
            pnpm check </dev/null
        else
            pnpm check </dev/null >/dev/null 2>&1
        fi || {
            echo "❌ pnpm check failed"
            return 1
        }
        [ "$VERBOSE" -eq 1 ] && echo "[BUILD_DEBUG] pnpm check succeeded" || true
    )
}

# -----------------------------
# Ctrl-C cleanup
# -----------------------------
cleanup() {
    echo "
Caught interrupt, killing background jobs and cleaning worktrees…" >&2
    # Kill all background jobs
    jobs -p | xargs -r kill 2>/dev/null || true
    git worktree prune >/dev/null 2>&1 || true
    rm -rf "$TMP_BASE" >/dev/null 2>&1 || true
    exit 130
}
trap cleanup INT

# -----------------------------
# Commit checker
# -----------------------------
check_commit() {
    local commit="$1"
    local worktree="$2"
    local log="$3"

    [ "$VERBOSE" -eq 1 ] && debug "check_commit() called for $commit" || true
    [ "$VERBOSE" -eq 1 ] && debug "  worktree: $worktree" || true
    [ "$VERBOSE" -eq 1 ] && debug "  log: $log" || true

    (
        set -euo pipefail
        echo "===== COMMIT $commit ====="

        [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Adding worktree at $worktree" || true
        git worktree add --force --detach "$worktree" "$commit" >/dev/null
        [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Worktree created, changing directory" || true
        cd "$worktree"
        [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] In worktree, PWD=$PWD" || true

        if [ -d rfc-edge-frontend ]; then
            [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Found rfc-edge-frontend directory" || true
            echo "→ Building frontend…"
            if ! build_frontend; then
                echo "❌ Frontend build failed"
                exit 1
            fi
            [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Frontend build completed successfully" || true
        else
            [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] No rfc-edge-frontend directory found, skipping frontend build" || true
        fi

        # Check if Rust files changed in this commit
        if git diff --name-only "${commit}^..${commit}" 2>/dev/null | grep -qE '\.(rs|toml)$|Cargo\.lock'; then
            [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Rust files changed, running cargo check" || true
            echo "→ Running cargo check…"
            if ! cargo check --quiet; then
                echo "❌ Cargo check failed"
                exit 1
            fi
            [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Cargo check completed successfully" || true
        else
            [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] No Rust files changed, skipping cargo check" || true
            echo "→ Skipping cargo check (no Rust changes)"
        fi

        echo "✓ OK"
    ) >"$log" 2>&1

    return $?
}

# -----------------------------
# Execution (parallel or sequential)
# -----------------------------
FAIL=0
TOTAL=${#COMMITS[@]}

# Export functions and variables for parallel execution
export -f check_commit build_frontend debug
export VERBOSE REPO_ROOT PNPM_STORE WORKTREES_DIR LOGS_DIR

# Process a single commit (for xargs)
process_commit() {
    local idx="$1"
    local commit="$2"
    local worktree="$WORKTREES_DIR/$commit"
    local log="$LOGS_DIR/$commit.log"

    echo "[ $((idx + 1)) / $TOTAL ] Checking $commit…"

    if check_commit "$commit" "$worktree" "$log"; then
        echo "✓ [ $((idx + 1)) / $TOTAL ] $commit passed"
        sed 's/^/    /' "$log"
        git worktree remove --force "$worktree" >/dev/null 2>&1 || true
        echo
        return 0
    else
        echo "❌ FAILED at commit $commit"
        sed 's/^/    /' "$log"
        echo
        return 1
    fi
}
export -f process_commit
export TOTAL

if [ "$JOBS" -eq 1 ]; then
    # Sequential execution
    for i in "${!COMMITS[@]}"; do
        if ! process_commit "$i" "${COMMITS[$i]}"; then
            FAIL=1
            break
        fi
    done
else
    # Parallel execution using xargs
    debug "Starting parallel execution with $JOBS jobs"

    # Create input for xargs: "index commit"
    for i in "${!COMMITS[@]}"; do
        echo "$i ${COMMITS[$i]}"
    done | xargs -P "$JOBS" -n 2 bash -c 'process_commit "$@"' _ || FAIL=1
fi

# -----------------------------
# Final output
# -----------------------------
if [ "$FAIL" -eq 1 ]; then
    echo "❌ Stopped early due to failure."
    debug "Cleaning up: removing $TMP_BASE"
else
    echo "🎉 All commits passed!"
    debug "All commits verified successfully"
    debug "Cleaning up: removing $TMP_BASE"
fi
rm -rf "$TMP_BASE" >/dev/null 2>&1
debug "Cleanup complete"