#!/bin/sh

OUTPUT_DIR="."
CASE="lower"
REPL_CHAR="_"
PREFIX=""
SUFFIX=".mp4"
MANUAL_TITLE=""
VERBOSE=0

usage() {
    cat << EOF
Usage: $(basename "$0") [OPTIONS]
Options:
    -l URL      Single video URL
    -f FILE     File containing URLs (one per line, # for comments)
                  If .csv: format is "url,title" where title must be quoted
                  If no ext/.txt: one URL per line
    -o DIR      Output directory (default: current directory)
    -c CASE     Case handling: none, lower, upper, title (default: lower)
-r CHAR     Replacement character for invalid chars (default: _)
    -T TITLE    Directly provide title (overrides fetching from URL)
    -v          Verbose output (warn on unquoted URLs)
    -h          Show this help
EOF
    exit 1
}

parse_title() {
    url="$1"
    yt-dlp --skip-download --print title "$url" 2>/dev/null
}

get_fallback_title() {
    url="$1"
    video_id=$(echo "$url" | grep -oE '/watch/[^/?]+' | cut -d'/' -f3)
    if [ -z "$video_id" ]; then
        video_id=$(echo "$url" | sed 's/.*\///')
    fi
    echo "tube_${video_id}"
}

format_filename() {
    title="$1"
    result="$title"

    case "$CASE" in
        lower)  result=$(echo "$result" | tr '[:upper:]' '[:lower:]') ;;
        upper)  result=$(echo "$result" | tr '[:lower:]' '[:upper:]') ;;
        title)  result=$(echo "$result" | awk '{for(i=1;i<=NF;i++) $i=toupper(substr($i,1,1)) tolower(substr($i,2));}1') ;;
    esac

    result=$(echo "$result" | sed "s/[^a-zA-Z0-9._-]/$REPL_CHAR/g")
    result=$(echo "$result" | sed "s/${REPL_CHAR}\{2,\}/${REPL_CHAR}/g")
    echo "$result"
}

is_csv() {
    file="$1"
    case "$file" in
        *.csv|*.CSV) return 0 ;;
        *)    return 1 ;;
    esac
}

validate_csv() {
    file="$1"
    lineno=0
    errors=0
    skipped_header=0

    while IFS= read -r line || [ -n "$line" ]; do
        lineno=$((lineno + 1))
        line=$(echo "$line" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')
        [ -z "$line" ] && continue

        case "$line" in
            \#*) continue ;;
        esac

        first_field=$(echo "$line" | cut -d',' -f1)

        if [ $skipped_header -eq 0 ] && [ $lineno -eq 1 ]; then
            if ! echo "$first_field" | grep -qi '^http'; then
                skipped_header=1
                continue
            fi
        fi
        skipped_header=1

        commas=$(echo "$line" | tr -cd ',' | wc -c)
        if [ "$commas" -eq 0 ]; then
            echo "Line $lineno: Missing comma separator (expected url,title)" >&2
            errors=$((errors + 1))
            continue
        fi

        first_char=$(echo "$line" | cut -c1)
        if [ "$first_char" = "\"" ]; then
            url=$(echo "$line" | sed 's/^"\([^"]*\)".*/\1/')
            rest=$(echo "$line" | sed 's/^"[^"]*",//')
        else
            url=$(echo "$line" | cut -d',' -f1)
            rest=$(echo "$line" | cut -d',' -f2-)

            if echo "$url" | grep -q ','; then
                echo "Line $lineno: URL contains comma - quote the URL if it contains commas." >&2
                errors=$((errors + 1))
                continue
            fi

            if [ -z "$url" ]; then
                echo "Line $lineno: Empty URL field" >&2
                errors=$((errors + 1))
                continue
            fi

            if [ "$VERBOSE" -eq 1 ]; then
                echo "Line $lineno: Warning - URL not quoted" >&2
            fi
        fi

        if [ -z "$rest" ]; then
            echo "Line $lineno: Missing title (must be quoted)" >&2
            errors=$((errors + 1))
            continue
        fi

        title_first=$(echo "$rest" | cut -c1)
        if [ "$title_first" != "\"" ]; then
            echo "Line $lineno: Title must be surrounded by quotes" >&2
            errors=$((errors + 1))
            continue
        fi
    done < "$file"

    if [ "$errors" -gt 0 ]; then
        echo "Error: CSV validation failed with $errors error(s). Please fix and retry." >&2
        return 1
    fi
    return 0
}

load_links() {
    file="$1"

    if is_csv "$file"; then
        if ! validate_csv "$file"; then
            exit 1
        fi
        skipped_header=0
        while IFS= read -r line || [ -n "$line" ]; do
            line=$(echo "$line" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')
            [ -z "$line" ] && continue
            case "$line" in \#*) continue ;; esac

            first_field=$(echo "$line" | cut -d',' -f1)

            if [ $skipped_header -eq 0 ]; then
                if ! echo "$first_field" | grep -qi '^http'; then
                    skipped_header=1
                    continue
                fi
            fi
            skipped_header=1

            url=$(echo "$line" | cut -d',' -f1)
            title=$(echo "$line" | cut -d',' -f2-)

            title=$(echo "$title" | sed 's/^"\(.*\)"$/\1/;s/[[:space:]]*$//')
            echo "${url}|${title}"
        done < "$file"
    else
        while IFS= read -r line || [ -n "$line" ]; do
            line=$(echo "$line" | sed 's/^[[:space:]]*//;s/[[:space:]]*$//')
            [ -z "$line" ] && continue
            case "$line" in \#*) continue ;; esac
            echo "${line}|"
        done < "$file"
    fi
}

while getopts "l:f:o:c:r:p:t:T:vh" opt; do
    case "$opt" in
        l) LINK="$OPTARG" ;;
        f) LINKFILE="$OPTARG" ;;
        o) OUTPUT_DIR="$OPTARG" ;;
        c) CASE="$OPTARG" ;;
        r) REPL_CHAR="$OPTARG" ;;
        p) PREFIX="$OPTARG" ;;
        t) SUFFIX="$OPTARG" ;;
        T) MANUAL_TITLE="$OPTARG" ;;
        v) VERBOSE=1 ;;
        h) usage ;;
        *) usage ;;
    esac
done
shift $((OPTIND - 1))

if [ -n "$LINKFILE" ]; then
    if [ ! -f "$LINKFILE" ]; then
        echo "Error: Link file not found: $LINKFILE" >&2
        exit 1
    fi
    ENTRIES=$(load_links "$LINKFILE")
elif [ -n "$LINK" ]; then
    ENTRIES="${LINK}|"
else
    usage
fi

echo "$ENTRIES" | grep -v '^$' | while read -r entry; do
    url=$(echo "$entry" | cut -d'|' -f1)
    manual_title=$(echo "$entry" | cut -d'|' -f2)

    [ -z "$url" ] && continue

    echo "Processing: $url"

    if [ -n "$manual_title" ]; then
        title="$manual_title"
    elif [ -n "$MANUAL_TITLE" ]; then
        title="$MANUAL_TITLE"
    else
        title=$(parse_title "$url")
        if [ -z "$title" ]; then
            echo "Warning: Could not parse title, using fallback" >&2
            title=$(get_fallback_title "$url")
        fi
    fi

    formatted=$(format_filename "$title")
    filename="${PREFIX}${formatted}${SUFFIX}"

    OUTPUT_PATH="$OUTPUT_DIR/$filename"
    OUTPUT_PATH=$(realpath "$OUTPUT_PATH")

    echo "Output: $OUTPUT_PATH"

    yt-dlp -f "bestvideo+bestaudio/best" -o "$OUTPUT_PATH" "$url"

    echo "Download complete: $filename"
    done