#!/usr/bin/env bash

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

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

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

# Initialize database with schema if it doesn't exist
init_db() {
    sqlite3 "$TASKS_DB" <<'EOF'
CREATE TABLE IF NOT EXISTS tasks (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    description TEXT NOT NULL,
    due_date TEXT,
    status TEXT DEFAULT 'pending',
    created_at TEXT DEFAULT CURRENT_TIMESTAMP,
    completed_at TEXT,
    project TEXT DEFAULT 'default'
);

CREATE INDEX IF NOT EXISTS idx_status ON tasks(status);
CREATE INDEX IF NOT EXISTS idx_due_date ON tasks(due_date);
CREATE INDEX IF NOT EXISTS idx_project ON tasks(project);
EOF
}

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 [-f file_name] \"task description\" [due_date]"
    echo ""
    echo "Multiple task lists:"
    echo "  Use -f to specify different task files (creates separate .db files)"
    echo "  Default file is 'tasks.db' if no -f flag is used"
    echo ""
    echo "Date formats: YYYY-MM-DD, 2025-08-10, tomorrow, next monday, etc."
    echo ""
    echo "Examples:"
    echo "  Basic usage:"
    echo "    ged \"Fix bug in project\"               # Add task"
    echo "    ged \"Call dentist\" tomorrow            # Add task with due date"
    echo "    ged                                     # List pending tasks"
    echo "    ged -d 1                                # Mark task 1 as done"
    echo "    ged -r 2 \"next friday\"                 # Reschedule task 2"
    echo ""
    echo "  Multiple task lists:"
    echo "    ged -f errands \"Buy groceries\"         # Add to errands.db"
    echo "    ged -f work -l                          # List work tasks"
    echo "    ged -f personal -s                      # Show personal stats"
    echo ""
    echo "  View completed and all tasks:"
    echo "    ged -c          (--completed)           # Show completed tasks"
    echo "    ged -a          (--all)                 # Show all tasks with status"
    echo "    ged -s          (--stats)               # Show statistics"
    echo ""
    echo "  Task management:"
    echo "    ged -x 3        (--remove)              # Permanently delete task 3"
    echo "    ged -p          (--purge)               # Remove tasks completed >30 days ago"
    echo "    ged -p 7        (--purge 7)             # Remove tasks completed >7 days ago"
    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
    
    # Initialize database
    init_db
    
    # Add task to database using safe SQL escaping
    local escapedDesc
    escapedDesc="${description//\'/\'\'}"  # Escape single quotes
    
    if [[ -n "$parsedDue" ]]; then
        sqlite3 "$TASKS_DB" "INSERT INTO tasks (description, due_date) VALUES ('$escapedDesc', '$parsedDue');"
    else
        sqlite3 "$TASKS_DB" "INSERT INTO tasks (description, due_date) VALUES ('$escapedDesc', NULL);"
    fi
    
    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() {
    # Initialize database
    init_db
    
    # Check if there are any pending tasks
    local taskCount
    taskCount=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks WHERE status = 'pending';")
    
    if [[ "$taskCount" -eq 0 ]]; then
        echo "No tasks found. Add some tasks to get started!"
        return
    fi
    
    echo "Git 'er Done task list"
    
    local displayNum=1
    
    # Get tasks with dates first, sorted by due_date
    while IFS='|' read -r description dueDate; do
        if [[ -n "$dueDate" ]]; then
            local formattedDate
            formattedDate=$(format_date "$dueDate")
            echo "$displayNum. $description Due by $formattedDate"
        else
            echo "$displayNum. $description"
        fi
        ((displayNum++))
    done < <(sqlite3 "$TASKS_DB" "SELECT description, due_date FROM tasks WHERE status = 'pending' ORDER BY 
        CASE WHEN due_date IS NULL THEN 1 ELSE 0 END,
        due_date ASC;")
}

mark_done() {
    local taskNum="$1"
    
    # Initialize database
    init_db
    
    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
    
    # Get the task ID by display number
    local taskId
    taskId=$(get_task_id_by_display_number "$taskNum")
    
    # Mark task as completed with timestamp
    sqlite3 "$TASKS_DB" "UPDATE tasks SET status = 'completed', completed_at = CURRENT_TIMESTAMP WHERE id = $taskId;"
    
    echo "Task $taskNum \"$taskDescription\" marked as done."
}

reschedule_task() {
    local taskNum="$1"
    local newDate="$2"
    
    # Initialize database
    init_db
    
    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
    
    # Get the task ID by display number
    local taskId
    taskId=$(get_task_id_by_display_number "$taskNum")
    
    # Update the task's due date
    sqlite3 "$TASKS_DB" "UPDATE tasks SET due_date = '$parsedDate' WHERE id = $taskId;"
    
    local formattedDate
    formattedDate=$(format_date "$parsedDate")
    echo "Task $taskNum \"$taskDescription\" rescheduled to $formattedDate."
}

get_task_by_display_number() {
    local targetNum="$1"
    
    # Initialize database
    init_db
    
    # Get the task description by row number from ordered query
    sqlite3 "$TASKS_DB" "SELECT description FROM tasks WHERE status = 'pending' ORDER BY 
        CASE WHEN due_date IS NULL THEN 1 ELSE 0 END,
        due_date ASC
        LIMIT 1 OFFSET $((targetNum - 1));"
}

get_task_id_by_display_number() {
    local targetNum="$1"
    
    # Initialize database
    init_db
    
    # Get the task ID by row number from ordered query
    sqlite3 "$TASKS_DB" "SELECT id FROM tasks WHERE status = 'pending' ORDER BY 
        CASE WHEN due_date IS NULL THEN 1 ELSE 0 END,
        due_date ASC
        LIMIT 1 OFFSET $((targetNum - 1));"
}



# Function to set database file based on -f flag
set_db_file() {
    local fileName="$1"
    if [[ -n "$fileName" ]]; then
        TASKS_DB="$TASKS_DIR/${fileName}.db"
    fi
}

# Remove a task permanently
remove_task() {
    local taskNum="$1"
    
    # Initialize database
    init_db
    
    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
    
    # Get the task ID by display number
    local taskId
    taskId=$(get_task_id_by_display_number "$taskNum")
    
    # Permanently delete the task
    sqlite3 "$TASKS_DB" "DELETE FROM tasks WHERE id = $taskId;"
    
    echo "Task $taskNum \"$taskDescription\" permanently removed."
}

# List completed tasks only
list_completed_tasks() {
    # Initialize database
    init_db
    
    # Check if there are any completed tasks
    local taskCount
    taskCount=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks WHERE status = 'completed';")
    
    if [[ "$taskCount" -eq 0 ]]; then
        echo "No completed tasks found."
        return
    fi
    
    echo "Completed tasks:"
    
    local displayNum=1
    
    # Get completed tasks sorted by completion date
    while IFS='|' read -r description dueDate completedAt; do
        local completedDate
        if [[ -n "$completedAt" ]]; then
            completedDate=$(date -d "$completedAt" "+%Y-%m-%d" 2>/dev/null || echo "$completedAt")
        else
            completedDate="unknown"
        fi
        
        if [[ -n "$dueDate" ]]; then
            local formattedDue
            formattedDue=$(format_date "$dueDate")
            echo "$displayNum. ✓ $description (was due $formattedDue) - completed $completedDate"
        else
            echo "$displayNum. ✓ $description - completed $completedDate"
        fi
        ((displayNum++))
    done < <(sqlite3 "$TASKS_DB" "SELECT description, due_date, completed_at FROM tasks WHERE status = 'completed' ORDER BY completed_at DESC;")
}

# List all tasks with status
list_all_tasks() {
    # Initialize database
    init_db
    
    # Check if there are any tasks
    local taskCount
    taskCount=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks;")
    
    if [[ "$taskCount" -eq 0 ]]; then
        echo "No tasks found."
        return
    fi
    
    echo "All tasks:"
    
    local displayNum=1
    
    # Get all tasks sorted by status (pending first), then by due date
    while IFS='|' read -r description dueDate status completedAt; do
        local statusIcon=""
        local statusText=""
        
        case "$status" in
            "pending")
                statusIcon="○"
                statusText=""
                ;;
            "completed")
                statusIcon="✓"
                local completedDate
                if [[ -n "$completedAt" ]]; then
                    completedDate=$(date -d "$completedAt" "+%m-%d" 2>/dev/null || echo "$completedAt")
                    statusText=" (done $completedDate)"
                else
                    statusText=" (done)"
                fi
                ;;
        esac
        
        if [[ -n "$dueDate" ]]; then
            local formattedDate
            formattedDate=$(format_date "$dueDate")
            echo "$displayNum. $statusIcon $description Due by $formattedDate$statusText"
        else
            echo "$displayNum. $statusIcon $description$statusText"
        fi
        ((displayNum++))
    done < <(sqlite3 "$TASKS_DB" "SELECT description, due_date, status, completed_at FROM tasks ORDER BY 
        CASE WHEN status = 'pending' THEN 0 ELSE 1 END,
        CASE WHEN due_date IS NULL THEN 1 ELSE 0 END,
        due_date ASC;")
}

# Show task statistics
show_stats() {
    # Initialize database
    init_db
    
    echo "Task Statistics:"
    echo "=================="
    
    # Get basic counts
    local totalTasks pendingTasks completedTasks
    totalTasks=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks;")
    pendingTasks=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks WHERE status = 'pending';")
    completedTasks=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks WHERE status = 'completed';")
    
    echo "Total tasks: $totalTasks"
    echo "Pending: $pendingTasks"
    echo "Completed: $completedTasks"
    
    if [[ "$totalTasks" -gt 0 ]]; then
        local completionRate
        completionRate=$(sqlite3 "$TASKS_DB" "SELECT ROUND(COUNT(*) * 100.0 / (SELECT COUNT(*) FROM tasks), 1) FROM tasks WHERE status = 'completed';")
        echo "Completion rate: ${completionRate}%"
    fi
    
    # Overdue tasks
    local overdueTasks
    overdueTasks=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks WHERE status = 'pending' AND due_date < date('now');")
    if [[ "$overdueTasks" -gt 0 ]]; then
        echo "⚠️  Overdue tasks: $overdueTasks"
    fi
    
    # Tasks due today
    local todayTasks
    todayTasks=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks WHERE status = 'pending' AND due_date = date('now');")
    if [[ "$todayTasks" -gt 0 ]]; then
        echo "📅 Due today: $todayTasks"
    fi
}

# Purge old completed tasks
purge_old_tasks() {
    local daysOld="${1:-30}"
    
    # Initialize database
    init_db
    
    if [[ ! "$daysOld" =~ ^[0-9]+$ ]]; then
        echo "Error: Days must be a number"
        return 1
    fi
    
    # Count tasks to be purged
    local tasksToDelete
    tasksToDelete=$(sqlite3 "$TASKS_DB" "SELECT COUNT(*) FROM tasks WHERE status = 'completed' AND completed_at < datetime('now', '-$daysOld days');")
    
    if [[ "$tasksToDelete" -eq 0 ]]; then
        echo "No completed tasks older than $daysOld days found."
        return
    fi
    
    echo "Found $tasksToDelete completed tasks older than $daysOld days."
    read -p "Are you sure you want to permanently delete them? (y/N): " -n 1 -r
    echo
    
    if [[ $REPLY =~ ^[Yy]$ ]]; then
        sqlite3 "$TASKS_DB" "DELETE FROM tasks WHERE status = 'completed' AND completed_at < datetime('now', '-$daysOld days');"
        echo "$tasksToDelete old completed tasks have been purged."
    else
        echo "Purge cancelled."
    fi
}

# Array of command line arguments
declare -A command=(
    [a]="List all tasks with their status (--all)."
    [c]="List completed tasks only (--completed)."
    [d:task_number]="Mark task as done."
    [f:file_name]="Use specified database file (without .db extension)."
    [h]="This help screen."
    [l]="List pending tasks (same as no arguments)."
    [p:days]="Remove completed tasks older than N days (--purge, default: 30)."
    [r:task_number:new_date]="Reschedule task to new date."
    [s]="Show task statistics (--stats)."
    [x:task_number]="Permanently delete a task (--remove)."
)

# Parse -f flag first if present
if [[ "$1" == "-f" ]]; then
    if [[ -z "$2" ]]; then
        echo "Error: File name required for -f option"
        exit 1
    fi
    set_db_file "$2"
    # Shift arguments to remove -f and filename
    shift 2
fi

# 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"
        ;;
    "-f")
        echo "Error: -f flag must be used as first argument"
        exit 1
        ;;
    "-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
        ;;
    "--remove"|"--rm"|"-x")
        if [[ -z "$2" ]]; then
            echo "Error: Task number required for --remove option"
            exit 1
        fi
        remove_task "$2"
        ;;
    "--completed"|"--done"|"-c")
        list_completed_tasks
        ;;
    "--all"|"-a")
        list_all_tasks
        ;;
    "--stats"|"-s")
        show_stats
        ;;
    "--purge"|"-p")
        purge_old_tasks "$2"
        ;;
    *)
        # Add new task
        add_task "$1" "$2"
        ;;
esac

exit 0