#!/bin/bash

# Check if file argument is provided
if [ $# -ne 1 ]; then
    echo "Usage: $0 <path_to_file>"
    exit 1
fi

FILE="$1"

# Check if file exists
if [ ! -f "$FILE" ]; then
    echo "Error: File '$FILE' not found"
    exit 1
fi

# Terminal control functions
hide_cursor() {
    printf '\033[?25l'
}

show_cursor() {
    printf '\033[?25h'
}

move_cursor() {
    printf '\033[%d;%dH' "$1" "$2"
}

clear_screen() {
    printf '\033[2J'
    printf '\033[H'
}

cleanup() {
    show_cursor
    clear_screen
    echo "Goodbye!"
    exit 0
}

# Trap to ensure cursor is restored on exit
trap cleanup EXIT INT TERM

# Hide cursor at start
hide_cursor

# Parse the file and store tasks
declare -a categories=()
declare -A tasks=()
declare -A checked=()
declare -a display_items=()  # Store display items in order
current_category=""
task_counter=0

while IFS= read -r line; do
    if [[ $line =~ ^@(.+)$ ]]; then
        current_category="${BASH_REMATCH[1]}"
        categories+=("$current_category")
        display_items+=("CATEGORY:$current_category")
    elif [[ -n "$line" && -n "$current_category" ]]; then
        task_key="${current_category}_${task_counter}"
        tasks["$task_key"]="$line"
        checked["$task_key"]=false
        display_items+=("TASK:$task_key")
        ((task_counter++))
    fi
done < "$FILE"

# Current selection
current_selection=0
total_items=${#display_items[@]}
header_lines=3

# Initial display
initial_display() {
    clear_screen
    echo "Checklist - Use ↑/↓ to navigate, SPACE to toggle, q to quit"
    echo "File: $FILE"
    echo "=================================================="
    
    for i in "${!display_items[@]}"; do
        item="${display_items[$i]}"
        if [[ $item =~ ^CATEGORY:(.+)$ ]]; then
            category="${BASH_REMATCH[1]}"
            echo "@$category"
        elif [[ $item =~ ^TASK:(.+)$ ]]; then
            task_key="${BASH_REMATCH[1]}"
            checkbox="[ ]"
            if [ "${checked[$task_key]}" = true ]; then
                checkbox="[✓]"
            fi
            echo "  $checkbox ${tasks[$task_key]}"
        fi
        echo  # Empty line after each item
    done
}

# Update single line
update_line() {
    local line_num=$((header_lines + 1 + ($1 * 2)))  # *2 because of empty lines
    move_cursor $line_num 1
    printf '\033[K'  # Clear line
    
    item="${display_items[$1]}"
    if [[ $item =~ ^CATEGORY:(.+)$ ]]; then
        category="${BASH_REMATCH[1]}"
        if [ $1 -eq $current_selection ]; then
            printf '\033[7m@%s\033[0m' "$category"
        else
            printf '@%s' "$category"
        fi
    elif [[ $item =~ ^TASK:(.+)$ ]]; then
        task_key="${BASH_REMATCH[1]}"
        checkbox="[ ]"
        if [ "${checked[$task_key]}" = true ]; then
            checkbox="[✓]"
        fi
        task_line="  $checkbox ${tasks[$task_key]}"
        if [ $1 -eq $current_selection ]; then
            printf '\033[7m%s\033[0m' "$task_line"
        else
            printf '%s' "$task_line"
        fi
    fi
}

# Update only the checkbox part of a task line
update_checkbox() {
    local line_num=$((header_lines + 1 + ($1 * 2)))
    local task_key="${BASH_REMATCH[1]}"
    
    item="${display_items[$1]}"
    if [[ $item =~ ^TASK:(.+)$ ]]; then
        task_key="${BASH_REMATCH[1]}"
        checkbox="[ ]"
        if [ "${checked[$task_key]}" = true ]; then
            checkbox="[✓]"
        fi
        
        # Move to checkbox position (column 3) and update just the checkbox
        move_cursor $line_num 3
        if [ $1 -eq $current_selection ]; then
            printf '\033[7m%s\033[0m' "$checkbox"
        else
            printf '%s' "$checkbox"
        fi
    fi
}

# Get the task key at current selection
get_current_task_key() {
    item="${display_items[$current_selection]}"
    if [[ $item =~ ^TASK:(.+)$ ]]; then
        echo "${BASH_REMATCH[1]}"
    else
        echo ""
    fi
}

# Show initial display
initial_display

# Highlight first item
update_line 0

# Main loop
prev_selection=0
while true; do
    # Read single character
    IFS= read -rsn1 input
    
    # Handle different input cases
    if [[ $input == $'\x1b' ]]; then
        # ESC sequence - read next two characters
        IFS= read -rsn2 input
        case $input in
            '[A')  # Up arrow
                if [ $current_selection -gt 0 ]; then
                    prev_selection=$current_selection
                    ((current_selection--))
                    update_line $prev_selection
                    update_line $current_selection
                fi
                ;;
            '[B')  # Down arrow
                if [ $current_selection -lt $((total_items - 1)) ]; then
                    prev_selection=$current_selection
                    ((current_selection++))
                    update_line $prev_selection
                    update_line $current_selection
                fi
                ;;
        esac
    elif [[ $input == ' ' ]]; then
        # Space bar - toggle checkbox
        task_key=$(get_current_task_key)
        if [ -n "$task_key" ]; then
            if [ "${checked[$task_key]}" = true ]; then
                checked["$task_key"]=false
            else
                checked["$task_key"]=true
            fi
            # Only update the checkbox, not the entire line
            update_checkbox $current_selection
        fi
    elif [[ $input == 'q' ]] || [[ $input == 'Q' ]]; then
        # Quit - cleanup will be called by trap
        exit 0
    fi
done