<?php

namespace App\Actions\Permissions;

use App\Enums\Permission;
use App\Models\PermissionAssignment;
use App\Models\Project;
use App\Models\Team;
use App\Models\User;
use Illuminate\Database\Eloquent\Builder;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\DB;
use InvalidArgumentException;

class PermissionService
{
    /**
     * @param  array<int, Permission|string>  $permissions
     */
    public function sync(Model $assignee, ?Model $scope, array $permissions): void
    {
        $normalizedPermissions = $this->normalizePermissions($permissions, $assignee, $scope);

        DB::transaction(function () use ($assignee, $normalizedPermissions, $scope): void {
            $this->assignmentQuery($assignee, $scope)->delete();

            if ($normalizedPermissions === []) {
                return;
            }

            PermissionAssignment::query()->insert(
                array_map(
                    fn (Permission $permission): array => [
                        'permission' => $permission->value,
                        'assignee_id' => $assignee->getKey(),
                        'assignee_type' => $assignee->getMorphClass(),
                        'created_at' => now(),
                        'scope_id' => $scope?->getKey(),
                        'scope_type' => $scope?->getMorphClass(),
                        'updated_at' => now(),
                    ],
                    $normalizedPermissions,
                ),
            );
        });
    }

    public function grant(Model $assignee, Permission|string $permission, ?Model $scope = null): void
    {
        $normalizedPermission = $this->normalizePermission($permission);
        $this->assertAssignmentContext($normalizedPermission, $assignee, $scope);

        $alreadyExists = $this->assignmentQuery($assignee, $scope)
            ->where('permission', $normalizedPermission->value)
            ->exists();

        if ($alreadyExists) {
            return;
        }

        PermissionAssignment::query()->create([
            'permission' => $normalizedPermission->value,
            'assignee_id' => $assignee->getKey(),
            'assignee_type' => $assignee->getMorphClass(),
            'scope_id' => $scope?->getKey(),
            'scope_type' => $scope?->getMorphClass(),
        ]);
    }

    public function revoke(Model $assignee, Permission|string $permission, ?Model $scope = null): void
    {
        $normalizedPermission = $this->normalizePermission($permission);
        $this->assertAssignmentContext($normalizedPermission, $assignee, $scope);

        $this->assignmentQuery($assignee, $scope)
            ->where('permission', $normalizedPermission->value)
            ->delete();
    }

    public function allows(User $user, Permission|string $permission, ?Model $scope = null): bool
    {
        $requiredPermission = $this->normalizePermission($permission);

        return collect($this->effectivePermissions($user, $scope))
            ->contains(fn (Permission $effectivePermission): bool => $effectivePermission === $requiredPermission);
    }

    /**
     * @return array<int, Permission>
     */
    public function effectivePermissions(User $user, ?Model $scope = null): array
    {
        if ($this->hasGlobalAdmin($user)) {
            return Permission::cases();
        }

        /** @var Collection<int, Permission> $permissions */
        $permissions = $this->relevantAssignments($user, $scope)
            ->map(fn (PermissionAssignment $assignment): Permission => $assignment->permission)
            ->values();

        return $this->expandPermissions($permissions->all());
    }

    /**
     * @return array<int, array{label: string, value: string}>
     */
    public function permissionOptions(Model|string $assignee, Model|string|null $scope): array
    {
        return Permission::options(
            Permission::assignableFor($assignee, $scope),
        );
    }

    /**
     * @return array<string, array<int, string>>
     */
    public function assignmentMap(string $assigneeClass, ?Model $scope = null): array
    {
        /** @var Model $assignee */
        $assignee = new $assigneeClass;

        /** @var Collection<int, PermissionAssignment> $assignments */
        $assignments = PermissionAssignment::query()
            ->select(['assignee_id', 'permission'])
            ->where('assignee_type', $assignee->getMorphClass())
            ->tap(fn (Builder $query): Builder => $this->applyScopeConstraint($query, $scope))
            ->orderBy('permission')
            ->get();

        return $assignments
            ->groupBy(fn (PermissionAssignment $assignment): int => (int) $assignment->assignee_id)
            ->map(fn (Collection $group): array => $group
                ->map(fn (PermissionAssignment $assignment): string => $assignment->permission->value)
                ->values()
                ->all())
            ->all();
    }

    /**
     * @return array<int, int>
     */
    public function viewableProjectIds(User $user): array
    {
        if ($this->hasGlobalAdmin($user)) {
            return Project::query()
                ->pluck('id')
                ->map(fn (mixed $projectId): int => (int) $projectId)
                ->all();
        }

        /** @var Collection<int, PermissionAssignment> $assignments */
        $assignments = PermissionAssignment::query()
            ->select(['scope_id', 'permission'])
            ->where('scope_type', (new Project)->getMorphClass())
            ->where(function (Builder $query) use ($user): void {
                $query->where(function (Builder $directAssignmentsQuery) use ($user): void {
                    $directAssignmentsQuery
                        ->where('assignee_type', $user->getMorphClass())
                        ->where('assignee_id', $user->getKey());
                });

                $teamIds = $user->teams()
                    ->pluck('teams.id')
                    ->map(fn (mixed $teamId): int => (int) $teamId)
                    ->all();

                if ($teamIds !== []) {
                    $query->orWhere(function (Builder $teamAssignmentsQuery) use ($teamIds): void {
                        $teamAssignmentsQuery
                            ->where('assignee_type', (new Team)->getMorphClass())
                            ->whereIn('assignee_id', $teamIds);
                    });
                }
            })
            ->get();

        return $assignments
            ->filter(fn (PermissionAssignment $assignment): bool => $assignment->permission->includes(Permission::ProjectRead))
            ->pluck('scope_id')
            ->filter()
            ->map(fn (mixed $projectId): int => (int) $projectId)
            ->unique()
            ->values()
            ->all();
    }

    /**
     * @return array<int, int>
     */
    public function manageableTeamIds(User $user): array
    {
        if ($this->hasGlobalAdmin($user)) {
            return Team::query()
                ->pluck('id')
                ->map(fn (mixed $teamId): int => (int) $teamId)
                ->all();
        }

        /** @var Collection<int, PermissionAssignment> $assignments */
        $assignments = PermissionAssignment::query()
            ->select(['scope_id', 'permission'])
            ->where('assignee_type', $user->getMorphClass())
            ->where('assignee_id', $user->getKey())
            ->where('scope_type', (new Team)->getMorphClass())
            ->get();

        return $assignments
            ->filter(fn (PermissionAssignment $assignment): bool => $assignment->permission->includes(Permission::TeamManage))
            ->pluck('scope_id')
            ->filter()
            ->map(fn (mixed $teamId): int => (int) $teamId)
            ->unique()
            ->values()
            ->all();
    }

    public function canManageAnyTeam(User $user): bool
    {
        return $this->manageableTeamIds($user) !== [];
    }

    private function hasGlobalAdmin(User $user): bool
    {
        return PermissionAssignment::query()
            ->where('assignee_type', $user->getMorphClass())
            ->where('assignee_id', $user->getKey())
            ->whereNull('scope_type')
            ->whereNull('scope_id')
            ->where('permission', Permission::GlobalAdmin->value)
            ->exists();
    }

    /**
     * @return Collection<int, PermissionAssignment>
     */
    private function relevantAssignments(User $user, ?Model $scope): Collection
    {
        $query = PermissionAssignment::query();
        $this->applyScopeConstraint($query, $scope);

        $query->where(function (Builder $permissionQuery) use ($scope, $user): void {
            $permissionQuery->where(function (Builder $directAssignmentsQuery) use ($user): void {
                $directAssignmentsQuery
                    ->where('assignee_type', $user->getMorphClass())
                    ->where('assignee_id', $user->getKey());
            });

            if ($scope instanceof Project) {
                $teamIds = $user->teams()
                    ->pluck('teams.id')
                    ->map(fn (mixed $teamId): int => (int) $teamId)
                    ->all();

                if ($teamIds !== []) {
                    $permissionQuery->orWhere(function (Builder $teamAssignmentsQuery) use ($teamIds): void {
                        $teamAssignmentsQuery
                            ->where('assignee_type', (new Team)->getMorphClass())
                            ->whereIn('assignee_id', $teamIds);
                    });
                }
            }
        });

        return $query->get();
    }

    /**
     * @param  array<int, Permission|string>  $permissions
     * @return array<int, Permission>
     */
    private function normalizePermissions(array $permissions, Model $assignee, ?Model $scope): array
    {
        return collect($permissions)
            ->map(fn (Permission|string $permission): Permission => $this->normalizePermission($permission))
            ->each(fn (Permission $permission): bool => $this->assertAssignmentContext($permission, $assignee, $scope))
            ->unique(fn (Permission $permission): string => $permission->value)
            ->values()
            ->all();
    }

    private function normalizePermission(Permission|string $permission): Permission
    {
        if ($permission instanceof Permission) {
            return $permission;
        }

        return Permission::from(trim($permission));
    }

    private function assertAssignmentContext(Permission $permission, Model $assignee, ?Model $scope): bool
    {
        if (! $permission->isAssignableTo($assignee) || ! $permission->matchesScope($scope)) {
            throw new InvalidArgumentException("The {$permission->value} permission cannot be assigned in this context.");
        }

        return true;
    }

    private function assignmentQuery(Model $assignee, ?Model $scope): Builder
    {
        $query = PermissionAssignment::query()
            ->where('assignee_type', $assignee->getMorphClass())
            ->where('assignee_id', $assignee->getKey());

        $this->applyScopeConstraint($query, $scope);

        return $query;
    }

    private function applyScopeConstraint(Builder $query, ?Model $scope): Builder
    {
        if ($scope === null) {
            return $query
                ->whereNull('scope_type')
                ->whereNull('scope_id');
        }

        return $query
            ->where('scope_type', $scope->getMorphClass())
            ->where('scope_id', $scope->getKey());
    }

    /**
     * @param  array<int, Permission>  $permissions
     * @return array<int, Permission>
     */
    private function expandPermissions(array $permissions): array
    {
        $expandedPermissions = [];

        foreach ($permissions as $permission) {
            $expandedPermissions[$permission->value] = $permission;

            foreach ($permission->impliedPermissions() as $impliedPermission) {
                $expandedPermissions[$impliedPermission->value] = $impliedPermission;
            }
        }

        return array_values($expandedPermissions);
    }
}