#!/usr/bin/env bash

# Git 'er Done - Simple Todo Manager
# Usage:
#   ged [task description] [due_date]  - Add a task
#   ged                                - List all tasks
#   ged -d <task_number>              - Mark task as done
#   ged -r <task_number> <new_date>   - Reschedule task

# Use XDG data directory or fallback
XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"
TASKS_DIR="$XDG_DATA_HOME/git-er-done"
TASKS_FILE="$TASKS_DIR/tasks"

# Create directory if it doesn't exist
mkdir -p "$TASKS_DIR"

help() {
    echo "${0##*/}"
    echo "Git 'er Done - Simple Todo Manager"
    echo ""
    echo "Usage:"
    echo "With no arguments, list all tasks."
    for i in "${!command[@]}" ; do
        if [[ "$i" == *:* ]]; then
            local flag="${i%%:*}"
            local params="${i#*:}"
            params="${params//:/ ><}"
            echo "-${flag} <${params}>: ${command[${i}]}"
        else
            echo "-${i}: ${command[${i}]}"
        fi
    done | sort
    echo ""
    echo "When adding tasks:"
    echo "  ged \"task description\" [due_date]"
    echo ""
    echo "Date formats: YYYY-MM-DD, 2025-08-10, tomorrow, next monday, etc."
    echo ""
    echo "Examples:"
    echo "  ged \"Fix bug in project\""
    echo "  ged \"Call dentist\" tomorrow"
    echo "  ged \"Submit report\" 2025-08-15"
    echo "  ged -d 1"
    echo "  ged -r 2 \"next friday\""
    exit 0
}

parse_date() {
    local inputDate="$1"
    if [[ -z "$inputDate" ]]; then
        echo ""
        return
    fi
    
    # If it's already in YYYY-MM-DD format, return it
    if [[ "$inputDate" =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]]; then
        echo "$inputDate"
        return
    fi
    
    # Use date command to parse natural language dates
    local parsedDate
    if parsedDate=$(date -d "$inputDate" +%Y-%m-%d 2>/dev/null); then
        echo "$parsedDate"
    else
        echo ""
    fi
}

format_date() {
    local dateStr="$1"
    if [[ -z "$dateStr" ]]; then
        echo ""
        return
    fi
    
    local formatted
    if formatted=$(date -d "$dateStr" "+%A, %B %d, %Y" 2>/dev/null); then
        echo "$formatted"
    else
        echo "$dateStr"
    fi
}

add_task() {
    local description="$1"
    local dueDate="$2"
    
    if [[ -z "$description" ]]; then
        echo "Error: Task description required"
        return 1
    fi
    
    local parsedDue=""
    if [[ -n "$dueDate" ]]; then
        parsedDue=$(parse_date "$dueDate")
        if [[ -z "$parsedDue" ]]; then
            echo "Error: Invalid date format '$dueDate'"
            return 1
        fi
    fi
    
    # Create tasks file if it doesn't exist
    touch "$TASKS_FILE"
    
    # Add task to file (format: description|due_date)
    echo "$description|$parsedDue" >> "$TASKS_FILE"
    
    if [[ -n "$parsedDue" ]]; then
        local formattedDate
        formattedDate=$(format_date "$parsedDue")
        echo "Task \"$description\" added, due by $formattedDate."
    else
        echo "Task \"$description\" added."
    fi
}

list_tasks() {
    if [[ ! -f "$TASKS_FILE" ]] || [[ ! -s "$TASKS_FILE" ]]; then
        echo "No tasks found. Add some tasks to get started!"
        return
    fi
    
    echo "Git 'er Done task list"
    
    # Read tasks, sort by due date (tasks with dates first, then tasks without)
    local tasksWithDates=()
    local tasksWithoutDates=()
    local lineNum=1
    
    while IFS='|' read -r description dueDate; do
        if [[ -n "$dueDate" ]]; then
            tasksWithDates+=("$lineNum|$description|$dueDate")
        else
            tasksWithoutDates+=("$lineNum|$description|")
        fi
        ((lineNum++))
    done < "$TASKS_FILE"
    
    # Sort tasks with dates by date
    if [[ ${#tasksWithDates[@]} -gt 0 ]]; then
        readarray -t tasksWithDates < <(printf '%s\n' "${tasksWithDates[@]}" | sort -t'|' -k3)
    fi
    
    local displayNum=1
    
    # Display tasks with dates first
    for task in "${tasksWithDates[@]}"; do
        IFS='|' read -r _ description dueDate <<< "$task"
        local formattedDate
        formattedDate=$(format_date "$dueDate")
        echo "$displayNum. $description Due by $formattedDate"
        ((displayNum++))
    done
    
    # Then display tasks without dates
    for task in "${tasksWithoutDates[@]}"; do
        IFS='|' read -r _ description _ <<< "$task"
        echo "$displayNum. $description"
        ((displayNum++))
    done
}

mark_done() {
    local taskNum="$1"
    
    if [[ ! -f "$TASKS_FILE" ]] || [[ ! -s "$TASKS_FILE" ]]; then
        echo "No tasks found."
        return 1
    fi
    
    if [[ ! "$taskNum" =~ ^[0-9]+$ ]]; then
        echo "Error: Task number must be a number"
        return 1
    fi
    
    # Get the task description for confirmation
    local taskDescription
    taskDescription=$(get_task_by_display_number "$taskNum")
    if [[ -z "$taskDescription" ]]; then
        echo "Error: Task $taskNum not found"
        return 1
    fi
    
    # Remove the task from the file
    local tempFile
    tempFile=$(mktemp)
    remove_task_by_display_number "$taskNum" > "$tempFile"
    mv "$tempFile" "$TASKS_FILE"
    
    echo "Task $taskNum \"$taskDescription\" marked as done and removed from list."
}

reschedule_task() {
    local taskNum="$1"
    local newDate="$2"
    
    if [[ ! -f "$TASKS_FILE" ]] || [[ ! -s "$TASKS_FILE" ]]; then
        echo "No tasks found."
        return 1
    fi
    
    if [[ ! "$taskNum" =~ ^[0-9]+$ ]]; then
        echo "Error: Task number must be a number"
        return 1
    fi
    
    local parsedDate
    parsedDate=$(parse_date "$newDate")
    if [[ -z "$parsedDate" ]]; then
        echo "Error: Invalid date format '$newDate'"
        return 1
    fi
    
    # Get the task description
    local taskDescription
    taskDescription=$(get_task_by_display_number "$taskNum")
    if [[ -z "$taskDescription" ]]; then
        echo "Error: Task $taskNum not found"
        return 1
    fi
    
    # Update the task
    local tempFile
    tempFile=$(mktemp)
    update_task_by_display_number "$taskNum" "$parsedDate" > "$tempFile"
    mv "$tempFile" "$TASKS_FILE"
    
    local formattedDate
    formattedDate=$(format_date "$parsedDate")
    echo "Task $taskNum \"$taskDescription\" rescheduled to $formattedDate."
}

get_task_by_display_number() {
    local targetNum="$1"
    local currentNum=1
    
    # Build sorted list like in list_tasks
    local tasksWithDates=()
    local tasksWithoutDates=()
    local lineNum=1
    
    while IFS='|' read -r description dueDate; do
        if [[ -n "$dueDate" ]]; then
            tasksWithDates+=("$lineNum|$description|$dueDate")
        else
            tasksWithoutDates+=("$lineNum|$description|")
        fi
        ((lineNum++))
    done < "$TASKS_FILE"
    
    if [[ ${#tasksWithDates[@]} -gt 0 ]]; then
        readarray -t tasksWithDates < <(printf '%s\n' "${tasksWithDates[@]}" | sort -t'|' -k3)
    fi
    
    # Check tasks with dates first
    for task in "${tasksWithDates[@]}"; do
        if [[ $currentNum -eq $targetNum ]]; then
            IFS='|' read -r _ description _ <<< "$task"
            echo "$description"
            return
        fi
        ((currentNum++))
    done
    
    # Then check tasks without dates
    for task in "${tasksWithoutDates[@]}"; do
        if [[ $currentNum -eq $targetNum ]]; then
            IFS='|' read -r _ description _ <<< "$task"
            echo "$description"
            return
        fi
        ((currentNum++))
    done
}

remove_task_by_display_number() {
    local targetNum="$1"
    local currentNum=1
    
    # Build sorted list and track original line numbers
    local tasksWithDates=()
    local tasksWithoutDates=()
    local lineNum=1
    
    while IFS='|' read -r description dueDate; do
        if [[ -n "$dueDate" ]]; then
            tasksWithDates+=("$lineNum|$description|$dueDate")
        else
            tasksWithoutDates+=("$lineNum|$description|")
        fi
        ((lineNum++))
    done < "$TASKS_FILE"
    
    if [[ ${#tasksWithDates[@]} -gt 0 ]]; then
        readarray -t tasksWithDates < <(printf '%s\n' "${tasksWithDates[@]}" | sort -t'|' -k3)
    fi
    
    local skipLine=0
    
    # Find which original line to skip
    for task in "${tasksWithDates[@]}"; do
        if [[ $currentNum -eq $targetNum ]]; then
            IFS='|' read -r origLine _ _ <<< "$task"
            skipLine=$origLine
            break
        fi
        ((currentNum++))
    done
    
    if [[ $skipLine -eq 0 ]]; then
        for task in "${tasksWithoutDates[@]}"; do
            if [[ $currentNum -eq $targetNum ]]; then
                IFS='|' read -r origLine _ _ <<< "$task"
                skipLine=$origLine
                break
            fi
            ((currentNum++))
        done
    fi
    
    # Output all lines except the one to skip
    lineNum=1
    while IFS='|' read -r description dueDate; do
        if [[ $lineNum -ne $skipLine ]]; then
            echo "$description|$dueDate"
        fi
        ((lineNum++))
    done < "$TASKS_FILE"
}

update_task_by_display_number() {
    local targetNum="$1"
    local newDueDate="$2"
    local currentNum=1
    
    # Build sorted list and track original line numbers
    local tasksWithDates=()
    local tasksWithoutDates=()
    local lineNum=1
    
    while IFS='|' read -r description dueDate; do
        if [[ -n "$dueDate" ]]; then
            tasksWithDates+=("$lineNum|$description|$dueDate")
        else
            tasksWithoutDates+=("$lineNum|$description|")
        fi
        ((lineNum++))
    done < "$TASKS_FILE"
    
    if [[ ${#tasksWithDates[@]} -gt 0 ]]; then
        readarray -t tasksWithDates < <(printf '%s\n' "${tasksWithDates[@]}" | sort -t'|' -k3)
    fi
    
    local updateLine=0
    local targetDescription=""
    
    # Find which original line to update
    for task in "${tasksWithDates[@]}"; do
        if [[ $currentNum -eq $targetNum ]]; then
            IFS='|' read -r origLine description _ <<< "$task"
            updateLine=$origLine
            targetDescription="$description"
            break
        fi
        ((currentNum++))
    done
    
    if [[ $updateLine -eq 0 ]]; then
        for task in "${tasksWithoutDates[@]}"; do
            if [[ $currentNum -eq $targetNum ]]; then
                IFS='|' read -r origLine description _ <<< "$task"
                updateLine=$origLine
                targetDescription="$description"
                break
            fi
            ((currentNum++))
        done
    fi
    
    # Output all lines, updating the target line
    lineNum=1
    while IFS='|' read -r description dueDate; do
        if [[ $lineNum -eq $updateLine ]]; then
            echo "$targetDescription|$newDueDate"
        else
            echo "$description|$dueDate"
        fi
        ((lineNum++))
    done < "$TASKS_FILE"
}

# Array of command line arguments
declare -A command=(
    [d:task_number]="Mark task as done and remove from list."
    [h]="This help screen."
    [r:task_number:new_date]="Reschedule task to new date."
    [l]="List all tasks (same as no arguments)."
)

# Main script logic with improved help but simple case parsing
case "$1" in
    "")
        list_tasks
        ;;
    "-h"|"--help")
        help
        ;;
    "-d")
        if [[ -z "$2" ]]; then
            echo "Error: Task number required for -d option"
            exit 1
        fi
        mark_done "$2"
        ;;
    "-r")
        if [[ -z "$2" ]] || [[ -z "$3" ]]; then
            echo "Error: Task number and new date required for -r option"
            exit 1
        fi
        reschedule_task "$2" "$3"
        ;;
    "-l")
        list_tasks
        ;;
    *)
        # Add new task
        add_task "$1" "$2"
        ;;
esac

exit 0