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

# Usage:
#   check-history.sh <start_offset> <count> [--verbose]
# Example:
#   check-history.sh 2 4   # checks commits 2,3,4,5
#   check-history.sh 5 1   # checks only commit 5
#   check-history.sh 1 1 --verbose   # verbose mode

VERBOSE=0
if [ $# -lt 2 ] || [ $# -gt 3 ]; then
    echo "Usage: $0 <start_offset_from_head> <count> [--verbose|-v]"
    exit 1
fi

if [ $# -eq 3 ] && { [ "$3" = "--verbose" ] || [ "$3" = "-v" ]; }; then
    VERBOSE=1
fi

# 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="$(( $1 - 1 ))"
COUNT="$2"
REPO_ROOT="$(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"

echo "Checking commits from offset $1 (HEAD~$START_OFFSET) for $COUNT commits…"
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 </dev/null
        else
            pnpm install --frozen-lockfile </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, cleaning worktrees…" >&2
    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

        echo "→ Running cargo check…"
        [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Starting cargo check" || true
        if ! cargo check --quiet; then
            echo "❌ Cargo check failed"
            exit 1
        fi
        [ "$VERBOSE" -eq 1 ] && echo "[CHECK_DEBUG] Cargo check completed successfully" || true

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

    return $?
}

# -----------------------------
# Sequential execution
# -----------------------------
FAIL=0
i=1
TOTAL=${#COMMITS[@]}
for commit in "${COMMITS[@]}"; do
    worktree="$WORKTREES_DIR/$commit"
    log="$LOGS_DIR/$commit.log"

    debug "===== Processing commit $i/$TOTAL ====="
    debug "Commit: $commit"
    debug "Worktree: $worktree"
    debug "Log file: $log"

    echo "[ $i / $TOTAL ] Checking $commit…"
    if ! check_commit "$commit" "$worktree" "$log"; then
        echo "❌ FAILED at commit $commit"
        sed 's/^/    /' "$log"
        FAIL=1
        break
    fi
    debug "Commit $commit passed"
    sed 's/^/    /' "$log"

    debug "Removing worktree at $worktree"
    git worktree remove --force "$worktree" >/dev/null 2>&1

    ((i++))
    echo
done

# -----------------------------
# 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"