#!/bin/bash
# Git OpenTimestamp Pre-Commit Backfill Hook
# Self-contained - no external dependencies
# Upgrades all historical proofs before each new commit

set -e

# Configuration
OUTPUT_DIR=".ots"
STATUS_CACHE="$OUTPUT_DIR/.attestation-cache"

# Ensure output directory exists
mkdir -p "$OUTPUT_DIR"

# Initialize cache file if it doesn't exist
if [ ! -f "$STATUS_CACHE" ]; then
    echo "# Attestation status cache" > "$STATUS_CACHE"
    echo "# Format: commit-hash:status:timestamp" >> "$STATUS_CACHE"
fi

# Function to get cached status
get_cached_status() {
    local commit="$1"
    local cache_line=$(grep "^$commit:" "$STATUS_CACHE" 2>/dev/null | tail -1)
    if [ -n "$cache_line" ]; then
        local status=$(echo "$cache_line" | cut -d: -f2)
        local timestamp=$(echo "$cache_line" | cut -d: -f3)
        local now=$(date +%s)
        local age=$((now - timestamp))
        # Cache valid for 1 hour (3600 seconds)
        if [ "$age" -lt 3600 ]; then
            echo "$status"
            return 0
        fi
    fi
    return 1
}

# Function to cache status
cache_status() {
    local commit="$1"
    local status="$2"
    local now=$(date +%s)
    echo "$commit:$status:$now" >> "$STATUS_CACHE"
}

# Function to generate proof using ots CLI
generate_proof() {
    local hash="$1"
    local output="$2"
    
    local temp_file=$(mktemp)
    local temp_ots="${temp_file}.ots"
    
    python3 -c "import sys; sys.stdout.buffer.write(bytes.fromhex('$hash'))" > "$temp_file"
    ots stamp "$temp_file" 2>/dev/null
    
    if [ -f "$temp_ots" ]; then
        mv "$temp_ots" "$output"
        rm -f "$temp_file"
        return 0
    else
        rm -f "$temp_file"
        return 1
    fi
}

# Function to check if proof is attested
is_attested() {
    local proof_file="$1"
    local pending_count=$(ots info "$proof_file" 2>&1 | grep -c "PendingAttestation" || echo "0")
    [ "$pending_count" -eq 0 ]
}

# Function to upgrade proof
upgrade_proof() {
    local proof_file="$1"
    ots upgrade "$proof_file" 2>/dev/null
}

echo "[ots] Backfilling proofs..."

# Get all commit hashes (oldest to newest)
COMMITS=$(git rev-list --reverse HEAD)
TOTAL=$(echo "$COMMITS" | wc -l)
CURRENT=0
UPDATED=0

for COMMIT in $COMMITS; do
    CURRENT=$((CURRENT + 1))
    PROOF_FILE="$OUTPUT_DIR/${COMMIT}.ots"
    
    # Skip verbose output for brevity
    if [ $CURRENT -le 3 ] || [ $CURRENT -eq $TOTAL ]; then
        echo "[ots] Processing commit $CURRENT/$TOTAL: ${COMMIT:0:8}"
    elif [ $CURRENT -eq 4 ]; then
        echo "[ots] ... processing remaining commits ..."
    fi
    
    if [ -f "$PROOF_FILE" ]; then
        # Check cached status first
        CACHED_STATUS=$(get_cached_status "$COMMIT" || echo "")
        
        if [ "$CACHED_STATUS" = "attested" ]; then
            continue
        fi
        
        # Check if already attested
        if is_attested "$PROOF_FILE"; then
            cache_status "$COMMIT" "attested"
            continue
        fi
        
        # Cache as pending
        cache_status "$COMMIT" "pending"
        
        # Skip upgrade if cache is fresh (< 10 min old)
        CACHE_LINE=$(grep "^$COMMIT:" "$STATUS_CACHE" | tail -1)
        CACHE_TIME=$(echo "$CACHE_LINE" | cut -d: -f3)
        NOW=$(date +%s)
        CACHE_AGE=$((NOW - CACHE_TIME))
        
        if [ "$CACHE_AGE" -lt 600 ]; then
            continue
        fi
        
        # Try to upgrade
        if upgrade_proof "$PROOF_FILE"; then
            cache_status "$COMMIT" "attested"
            UPDATED=$((UPDATED + 1))
        fi
    else
        # Generate new proof
        if generate_proof "$COMMIT" "$PROOF_FILE"; then
            cache_status "$COMMIT" "pending"
            UPDATED=$((UPDATED + 1))
        fi
    fi
done

# Update latest proof symlink
LATEST_COMMIT=$(git rev-parse HEAD)
if [ -f "$OUTPUT_DIR/${LATEST_COMMIT}.ots" ]; then
    cp "$OUTPUT_DIR/${LATEST_COMMIT}.ots" "$OUTPUT_DIR/proof.ots"
fi

# Save commit chain
rm -f "$OUTPUT_DIR/commit-chain.txt"
git rev-list HEAD | while read COMMIT; do
    PREV=$(git rev-parse ${COMMIT}^1 2>/dev/null || echo "")
    if [ -n "$PREV" ]; then
        echo "$COMMIT:$PREV" >> "$OUTPUT_DIR/commit-chain.txt"
    fi
done

echo "[ots] Backfill complete: $UPDATED proofs updated"