#!/bin/bash
#
# note that this tool uses pdfresurrect -w, which creates version directories
# and extracts version files. to avoid modifying your directory structure, it's
# a good idea to run this script in a copy of your project directory.
#
# deps: qpdf, pdfresurrect

LOG_FILE="./resurrection_log.txt"
FAILURE_LOG="./resurrection_failures.log"

echo "--- Starting PDF resurrection scan ---" | tee "$LOG_FILE"
echo "Diffs of modified objects will be logged directly to: $LOG_FILE" | tee -a "$LOG_FILE"
echo "--------------------------------------" | tee -a "$LOG_FILE"

# reset failure log
> "$FAILURE_LOG"

find . -type f -iname "*.pdf" -not -iname "*_text.pdf" -not -path "*/*-versions/*" | while read -r FULL_PATH; do

    FILE_DIR=$(dirname "$FULL_PATH")
    FILE_NAME=$(basename "$FULL_PATH")
    BASE_NAME="${FILE_NAME%.*}" # filename w/o ext

    echo "Checking: $FULL_PATH"

    (
        cd "$FILE_DIR" || { echo "ERROR: Cannot access $FILE_DIR" >> "$FAILURE_LOG"; exit 1; }

        VERSION_COUNT_OUTPUT=$(pdfresurrect -q "$FILE_NAME" 2>/dev/null)
        EXIT_CODE=$?

        if [ "$EXIT_CODE" -ne 0 ]; then
            echo "Failed to run pdfresurrect -q on $FULL_PATH (Exit $EXIT_CODE)." >> "$FAILURE_LOG"
            exit 1
        fi

        VERSION_COUNT=$(echo "$VERSION_COUNT_OUTPUT" | grep -oP ': \K\d+' | tail -n 1)

        if [ "$VERSION_COUNT" -le 1 ]; then
            echo "  -> No history found ($VERSION_COUNT version(s))."
            exit 0
        fi

        echo "  -> History detected ($VERSION_COUNT versions). Extracting..."

        pdfresurrect -w "$FILE_NAME" > /dev/null 2>&1

        SUMMARY_FILE="$BASE_NAME-versions/$BASE_NAME-versions.summary"

        if [ ! -f "$SUMMARY_FILE" ]; then
            echo "  -> CRITICAL ERROR: Summary file not created at $SUMMARY_FILE, skipping diff."
            exit 1
        fi

        RAW_MODIFIED_OBJECTS=$(awk '/: --[DM]--/ { print $4, $7 }' "$SUMMARY_FILE" | sort -u)

        echo "  -> Raw D/M object list (V OBJ):"
        echo "$RAW_MODIFIED_OBJECTS" | while read -r line; do
            [ -n "$line" ] && echo "     - $line"
        done

        while IFS= read -r line ; do
            CURRENT_VERSION=$(echo "$line" | awk '{print $1}')
            OBJ_ID=$(echo "$line" | awk '{print $2}')
            
            if [ -z "$CURRENT_VERSION" ] || [ -z "$OBJ_ID" ]; then
                [ -n "$line" ] && echo "   -> WARNING: Parsed empty version/object pair from line: \"$line\". Skipping."
                continue
            fi

            if ! [[ "$CURRENT_VERSION" =~ ^[0-9]+$ ]] || ! [[ "$OBJ_ID" =~ ^[0-9]+$ ]]; then
                echo "   -> ERROR: Parsed invalid numbers ($CURRENT_VERSION : $OBJ_ID) from summary. Skipping."
                continue
            fi

            if [ "$CURRENT_VERSION" -eq 1 ]; then
                 echo "   -> Skipping Object $OBJ_ID: Current version is V1, no V0 exists to diff against."
                 continue
            fi
            
            PREV_VERSION=$((CURRENT_VERSION - 1))

            V1_FILE="$BASE_NAME-versions/$BASE_NAME-version-$PREV_VERSION.pdf"
            V2_FILE="$BASE_NAME-versions/$BASE_NAME-version-$CURRENT_VERSION.pdf"
    
            TEMP_V1=$(mktemp)
            TEMP_V2=$(mktemp)

            qpdf --show-object="$OBJ_ID" --unfilter -- "$V1_FILE" > "$TEMP_V1" 2>/dev/null
            qpdf --show-object="$OBJ_ID" --unfilter -- "$V2_FILE" > "$TEMP_V2" 2>/dev/null

            if [ ! -s "$TEMP_V1" ] || [ ! -s "$TEMP_V2" ]; then
                if [ ! -s "$TEMP_V1" ]; then
                    qpdf --show-object="$OBJ_ID" -- "$V1_FILE" > "$TEMP_V1" 2>/dev/null
                fi
                
                if [ ! -s "$TEMP_V2" ]; then
                    qpdf --show-object="$OBJ_ID" -- "$V2_FILE" > "$TEMP_V2" 2>/dev/null
                fi
            fi
            if [ ! -s "$TEMP_V1" ] || [ ! -s "$TEMP_V2" ]; then
                echo "   -> NOTE: Object $OBJ_ID (V$PREV_VERSION or V$CURRENT_VERSION) extraction failed or produced empty output. Skipping diff."
                rm "$TEMP_V1" "$TEMP_V2"
                continue
            fi

            if diff -u "$TEMP_V1" "$TEMP_V2" >/dev/null ; then
                echo "   -> Object $OBJ_ID: No difference detected (V$PREV_VERSION vs V$CURRENT_VERSION)."
            else
                echo -e "\n\n--- DIFF START: $FULL_PATH | Object $OBJ_ID (V$PREV_VERSION vs V$CURRENT_VERSION) ---"
                echo "Note: Output extracted as raw PDF content for reliable comparison."
                diff -u "$TEMP_V1" "$TEMP_V2"
                echo "--- DIFF END: Object $OBJ_ID ---\n"
                DIFF_FOUND=1
            fi


            rm "$TEMP_V1" "$TEMP_V2"
        done < <(echo "$RAW_MODIFIED_OBJECTS")


    ) | tee -a "$LOG_FILE"

    if [ ${PIPESTATUS[0]} -ne 0 ]; then
        echo "Failed to process $FULL_PATH (See $FAILURE_LOG and $LOG_FILE)"
    fi
done
echo "----------------------------------------------------" | tee -a "$LOG_FILE"
echo "Scan complete. Check $LOG_FILE for inline object diffs." | tee -a "$LOG_FILE"
echo "Check $FAILURE_LOG for files that failed processing." | tee -a "$LOG_FILE"