<?php

namespace App\Http\Controllers\Api\V1;

use App\Http\Controllers\Controller;
use App\Models\Feature;
use App\Models\Inspection;
use App\Models\Issue;
use App\Models\IssueComment;
use App\Models\IssueTask;
use App\Models\Phase;
use App\Models\ProgressUpdate;
use App\Models\Project;
use App\Models\SyncLog;
use App\Models\User;
use Carbon\Carbon;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Validator;

class SyncController extends Controller
{
    /**
     * Push a batch of offline mutations. Returns a per-operation result
     * (applied | duplicate | conflict | error). Never aborts the whole batch.
     *
     * Identity:
     *  - create ops → the new record stores the client-generated `uuid` (idempotent).
     *  - update ops → target identified by `data.id` (server id); last-write-wins.
     */
    public function sync(Request $request)
    {
        $data = $request->validate([
            'operations'                      => ['required', 'array'],
            'operations.*.entity'             => ['required', 'string'],
            'operations.*.op'                 => ['required', 'string'],
            'operations.*.uuid'               => ['required', 'uuid'],
            'operations.*.data'               => ['required', 'array'],
            'operations.*.client_updated_at'  => ['nullable', 'date'],
        ]);

        $user = $request->user();
        $results = [];

        foreach ($data['operations'] as $op) {
            $results[] = $this->handle($user, $op);
        }

        return response()->json(['results' => $results]);
    }

    private function handle(User $user, array $op): array
    {
        $uuid = $op['uuid'];

        // Op-level idempotency: if this operation was already applied, replay its result.
        $prior = SyncLog::where('op_uuid', $uuid)
            ->where('entity', $op['entity'])->where('op', $op['op'])->first();
        if ($prior) {
            return ['uuid' => $uuid, 'status' => 'duplicate', 'server_id' => $prior->server_id];
        }

        try {
            $result = match ($op['entity'] . '.' . $op['op']) {
                'progress_update.create' => $this->progressUpdateCreate($user, $uuid, $op),
                'inspection.create'      => $this->inspectionCreate($user, $uuid, $op),
                'issue.create'           => $this->issueCreate($user, $uuid, $op),
                'issue.update'           => $this->issueUpdate($user, $uuid, $op),
                'issue_task.create'      => $this->issueTaskCreate($user, $uuid, $op),
                'issue_task.update'      => $this->issueTaskUpdate($user, $uuid, $op),
                'issue_comment.create'   => $this->issueCommentCreate($user, $uuid, $op),
                'feature.update'         => $this->featureUpdate($user, $uuid, $op),
                default                  => $this->error($uuid, 'unsupported entity/op: ' . $op['entity'] . '.' . $op['op']),
            };
        } catch (\Throwable $e) {
            $result = $this->error($uuid, $e->getMessage());
        }

        // Record only terminal successes so conflicts/errors can be safely retried.
        if ($result['status'] === 'applied') {
            SyncLog::create([
                'user_id'   => $user->id,
                'op_uuid'   => $uuid,
                'entity'    => $op['entity'],
                'op'        => $op['op'],
                'status'    => 'applied',
                'server_id' => $result['server_id'] ?? null,
            ]);
        }

        return $result;
    }

    // ── progress_update.create ───────────────────────────────────────────────────

    private function progressUpdateCreate(User $user, string $uuid, array $op): array
    {
        if ($existing = ProgressUpdate::where('uuid', $uuid)->first()) {
            return $this->duplicate($uuid, $existing->id);
        }

        $v = Validator::make($op['data'], [
            'phase_id' => ['required', 'integer', 'exists:phases,id'],
            'progress' => ['required', 'integer', 'min:0', 'max:100'],
            'comment'  => ['nullable', 'string'],
            'location' => ['nullable', 'array'],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $phase = Phase::with('project')->findOrFail($d['phase_id']);
        if (! $this->canAccess($user, $phase->project) || ! $user->can('update progress')) {
            return $this->error($uuid, 'forbidden');
        }

        $pu = ProgressUpdate::create([
            'uuid'              => $uuid,
            'phase_id'          => $phase->id,
            'user_id'           => $user->id,
            'progress_percent'  => $d['progress'],
            'comment'           => $d['comment'] ?? null,
            'location'          => $d['location'] ?? null,
            'client_updated_at' => $op['client_updated_at'] ?? null,
        ]);

        $phase->progress_percent = $d['progress'];
        $phase->save();

        return $this->applied($uuid, $pu->id);
    }

    // ── inspection.create ──────────────────────────────────────────────────────────

    private function inspectionCreate(User $user, string $uuid, array $op): array
    {
        if ($existing = Inspection::where('uuid', $uuid)->first()) {
            return $this->duplicate($uuid, $existing->id);
        }

        $v = Validator::make($op['data'], [
            'feature_id'  => ['required', 'integer', 'exists:features,id'],
            'template_id' => ['nullable', 'integer', 'exists:inspection_templates,id'],
            'data'        => ['nullable', 'array'],
            'status'      => ['nullable', 'string'],
            'result'      => ['nullable', 'string'],
            'notes'       => ['nullable', 'string'],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $feature = Feature::with('layer.phase.project')->findOrFail($d['feature_id']);
        $project = $feature->layer?->phase?->project;
        if (! $this->canAccess($user, $project) || ! $user->can('create inspections')) {
            return $this->error($uuid, 'forbidden');
        }

        $inspection = Inspection::create([
            'uuid'              => $uuid,
            'project_id'        => $project->id,
            'layer_id'          => $feature->layer_id,
            'feature_id'        => $feature->id,
            'template_id'       => $d['template_id'] ?? null,
            'user_id'           => $user->id,
            'data'              => $d['data'] ?? [],
            'status'            => $d['status'] ?? 'completed',
            'result'            => $d['result'] ?? null,
            'notes'             => $d['notes'] ?? null,
            'client_updated_at' => $op['client_updated_at'] ?? null,
        ]);

        return $this->applied($uuid, $inspection->id);
    }

    // ── issue.create / issue.update ──────────────────────────────────────────────────

    private function issueCreate(User $user, string $uuid, array $op): array
    {
        if ($existing = Issue::where('uuid', $uuid)->first()) {
            return $this->duplicate($uuid, $existing->id);
        }

        $v = Validator::make($op['data'], [
            'project_id'  => ['required', 'integer', 'exists:projects,id'],
            'feature_id'  => ['nullable', 'integer', 'exists:features,id'],
            'title'       => ['required', 'string', 'max:255'],
            'description' => ['nullable', 'string'],
            'priority'    => ['nullable', 'in:' . implode(',', Issue::PRIORITIES)],
            'status'      => ['nullable', 'in:' . implode(',', Issue::STATUSES)],
            'type'        => ['nullable', 'in:' . implode(',', Issue::TYPES)],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $project = Project::find($d['project_id']);
        if (! $this->canAccess($user, $project) || ! $user->can('create issues')) {
            return $this->error($uuid, 'forbidden');
        }

        $issue = Issue::create([
            'uuid'              => $uuid,
            'project_id'        => $project->id,
            'feature_id'        => $d['feature_id'] ?? null,
            'title'             => $d['title'],
            'description'       => $d['description'] ?? null,
            'priority'          => $d['priority'] ?? 'medium',
            'status'            => $d['status'] ?? 'open',
            'type'              => $d['type'] ?? 'other',
            'reported_by'       => $user->id,
            'client_updated_at' => $op['client_updated_at'] ?? null,
        ]);

        return $this->applied($uuid, $issue->id);
    }

    private function issueUpdate(User $user, string $uuid, array $op): array
    {
        $v = Validator::make($op['data'], [
            'id'               => ['required', 'integer', 'exists:issues,id'],
            'title'            => ['nullable', 'string', 'max:255'],
            'description'      => ['nullable', 'string'],
            'priority'         => ['nullable', 'in:' . implode(',', Issue::PRIORITIES)],
            'status'           => ['nullable', 'in:' . implode(',', Issue::STATUSES)],
            'type'             => ['nullable', 'in:' . implode(',', Issue::TYPES)],
            'assigned_to'      => ['nullable', 'integer', 'exists:users,id'],
            'resolution_notes' => ['nullable', 'string'],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $issue = Issue::with('project')->findOrFail($d['id']);
        if (! $this->canAccess($user, $issue->project) || ! $user->can('edit issues')) {
            return $this->error($uuid, 'forbidden');
        }

        if ($conflict = $this->conflict($uuid, $issue, $op)) {
            return $conflict;
        }

        $issue->fill(collect($d)->except('id')->toArray());
        if (in_array($issue->status, ['resolved', 'closed'], true) && ! $issue->resolved_at) {
            $issue->resolved_at = now();
        }
        $issue->client_updated_at = $op['client_updated_at'] ?? null;
        $issue->save();

        return $this->applied($uuid, $issue->id);
    }

    // ── issue_task.create / issue_task.update ──────────────────────────────────────

    private function issueTaskCreate(User $user, string $uuid, array $op): array
    {
        if ($existing = IssueTask::where('uuid', $uuid)->first()) {
            return $this->duplicate($uuid, $existing->id);
        }

        $v = Validator::make($op['data'], [
            'issue_id'    => ['required', 'integer', 'exists:issues,id'],
            'title'       => ['required', 'string', 'max:255'],
            'assigned_to' => ['nullable', 'integer', 'exists:users,id'],
            'due_date'    => ['nullable', 'date'],
            'is_done'     => ['nullable', 'boolean'],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $issue = Issue::with('project')->findOrFail($d['issue_id']);
        if (! $this->canAccess($user, $issue->project) || ! $user->can('edit issues')) {
            return $this->error($uuid, 'forbidden');
        }

        $done = $d['is_done'] ?? false;
        $task = IssueTask::create([
            'uuid'              => $uuid,
            'issue_id'          => $issue->id,
            'title'             => $d['title'],
            'assigned_to'       => $d['assigned_to'] ?? null,
            'due_date'          => $d['due_date'] ?? null,
            'is_done'           => $done,
            'done_at'           => $done ? now() : null,
            'done_by'           => $done ? $user->id : null,
            'order'             => ((int) $issue->tasks()->max('order')) + 1,
            'client_updated_at' => $op['client_updated_at'] ?? null,
        ]);

        return $this->applied($uuid, $task->id);
    }

    private function issueTaskUpdate(User $user, string $uuid, array $op): array
    {
        $v = Validator::make($op['data'], [
            'id'          => ['required', 'integer', 'exists:issue_tasks,id'],
            'title'       => ['nullable', 'string', 'max:255'],
            'assigned_to' => ['nullable', 'integer', 'exists:users,id'],
            'due_date'    => ['nullable', 'date'],
            'is_done'     => ['nullable', 'boolean'],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $task = IssueTask::with('issue.project')->findOrFail($d['id']);
        if (! $this->canAccess($user, $task->issue?->project) || ! $user->can('edit issues')) {
            return $this->error($uuid, 'forbidden');
        }

        if ($conflict = $this->conflict($uuid, $task, $op)) {
            return $conflict;
        }

        if (array_key_exists('is_done', $d)) {
            $task->is_done = (bool) $d['is_done'];
            $task->done_at = $d['is_done'] ? ($task->done_at ?? now()) : null;
            $task->done_by = $d['is_done'] ? ($task->done_by ?? $user->id) : null;
        }
        $task->fill(collect($d)->only('title', 'assigned_to', 'due_date')->toArray());
        $task->client_updated_at = $op['client_updated_at'] ?? null;
        $task->save();

        return $this->applied($uuid, $task->id);
    }

    // ── issue_comment.create ────────────────────────────────────────────────────────

    private function issueCommentCreate(User $user, string $uuid, array $op): array
    {
        if ($existing = IssueComment::where('uuid', $uuid)->first()) {
            return $this->duplicate($uuid, $existing->id);
        }

        $v = Validator::make($op['data'], [
            'issue_id' => ['required', 'integer', 'exists:issues,id'],
            'body'     => ['required', 'string', 'max:5000'],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $issue = Issue::with('project')->findOrFail($d['issue_id']);
        if (! $this->canAccess($user, $issue->project) || ! $user->can('view issues')) {
            return $this->error($uuid, 'forbidden');
        }

        $comment = IssueComment::create([
            'uuid'              => $uuid,
            'issue_id'          => $issue->id,
            'user_id'           => $user->id,
            'body'              => $d['body'],
            'client_updated_at' => $op['client_updated_at'] ?? null,
        ]);

        return $this->applied($uuid, $comment->id);
    }

    // ── feature.update ────────────────────────────────────────────────────────────

    private function featureUpdate(User $user, string $uuid, array $op): array
    {
        $v = Validator::make($op['data'], [
            'id'          => ['required', 'integer', 'exists:features,id'],
            'status'      => ['nullable', 'string'],
            'progress'    => ['nullable', 'integer', 'min:0', 'max:100'],
            'responsible' => ['nullable', 'string'],
        ]);
        if ($v->fails()) {
            return $this->error($uuid, 'validation: ' . $v->errors()->first());
        }
        $d = $v->validated();

        $feature = Feature::with('layer.phase.project')->findOrFail($d['id']);
        $project = $feature->layer?->phase?->project;
        if (! $this->canAccess($user, $project) || ! $user->can('update progress')) {
            return $this->error($uuid, 'forbidden');
        }

        if ($conflict = $this->conflict($uuid, $feature, $op)) {
            return $conflict;
        }

        $feature->fill(collect($d)->except('id')->toArray());
        $feature->client_updated_at = $op['client_updated_at'] ?? null;
        $feature->save();

        // Mirror web behaviour: recompute the phase progress from its features.
        if ($phase = $feature->layer?->phase) {
            $phase->progress_percent = (int) round($phase->features()->avg('progress') ?: 0);
            $phase->save();
        }

        return $this->applied($uuid, $feature->id);
    }

    // ── Helpers ──────────────────────────────────────────────────────────────────────

    private function canAccess(User $user, ?Project $project): bool
    {
        if (! $project) {
            return false;
        }
        return $user->can('manage all')
            || $project->users()->where('user_id', $user->id)->exists();
    }

    /**
     * Last-write-wins conflict detection: if the server row was updated after the
     * client's edit, reject with the current server value.
     */
    private function conflict(string $uuid, $model, array $op): ?array
    {
        if (empty($op['client_updated_at'])) {
            return null;
        }
        $clientAt = Carbon::parse($op['client_updated_at']);
        if ($model->updated_at && $model->updated_at->gt($clientAt)) {
            return [
                'uuid'   => $uuid,
                'status' => 'conflict',
                'server' => $model->fresh()->toArray(),
            ];
        }
        return null;
    }

    private function applied(string $uuid, int $id): array
    {
        return ['uuid' => $uuid, 'status' => 'applied', 'server_id' => $id];
    }

    private function duplicate(string $uuid, int $id): array
    {
        return ['uuid' => $uuid, 'status' => 'duplicate', 'server_id' => $id];
    }

    private function error(string $uuid, string $message): array
    {
        return ['uuid' => $uuid, 'status' => 'error', 'error' => $message];
    }
}