<?php

namespace Modules\TimelineScheduling\Services;

use Illuminate\Support\Collection;
use Modules\ProjectManagement\Models\Task;
use Modules\TimelineScheduling\Models\TaskDependency;

class GanttDataTransformer
{
    /**
     * Transform project tasks + dependencies into Gantt-chart-ready JSON.
     * Compatible with Frappe Gantt / similar chart libraries.
     */
    public function transform(int $projectId): array
    {
        $tasks = Task::where('project_id', $projectId)
            ->select('id', 'ulid', 'name', 'status', 'start_date', 'end_date', 'priority')
            ->orderBy('start_date')
            ->get();

        $dependencies = TaskDependency::whereIn('task_id', $tasks->pluck('id'))
            ->get()
            ->groupBy('task_id');

        $ganttTasks = $tasks->map(function (Task $task) use ($dependencies) {
            $deps = $dependencies->get($task->id, collect());
            $depStrings = $deps->map(fn($d) => "task-{$d->predecessor_id}")->implode(', ');

            return [
                'id' => "task-{$task->id}",
                'name' => $task->name,
                'start' => $task->start_date?->format('Y-m-d') ?? now()->format('Y-m-d'),
                'end' => $task->end_date?->format('Y-m-d') ?? now()->addDays(7)->format('Y-m-d'),
                'progress' => $this->statusToProgress($task->status),
                'dependencies' => $depStrings ?: null,
                'custom_class' => $this->statusToClass($task->status),
                'meta' => [
                    'task_id' => $task->id,
                    'status' => $task->status,
                    'priority' => $task->priority,
                ],
            ];
        });

        return $ganttTasks->values()->toArray();
    }

    private function statusToProgress(string $status): int
    {
        return match ($status) {
            'completed' => 100,
            'in_progress' => 50,
            'on_hold' => 25,
            default => 0,
        };
    }

    private function statusToClass(string $status): string
    {
        return match ($status) {
            'completed' => 'bar-completed',
            'in_progress' => 'bar-in-progress',
            'on_hold' => 'bar-on-hold',
            default => 'bar-pending',
        };
    }
}