package service

import (
	"context"

	"github.com/google/uuid"

	"github.com/vasyakrg/dns-autoresolver/internal/crypto"
	"github.com/vasyakrg/dns-autoresolver/internal/diff"
	"github.com/vasyakrg/dns-autoresolver/internal/provider"
	"github.com/vasyakrg/dns-autoresolver/internal/provider/registry"
	"github.com/vasyakrg/dns-autoresolver/internal/store/dto"
)

// DomainRef is the minimal data the service needs about a domain.
type DomainRef struct {
	ZoneID    string
	Provider  string
	SecretEnc string
	Template  dto.TemplateDoc
}

type Loader interface {
	LoadDomain(ctx context.Context, projectID, domainID uuid.UUID) (DomainRef, error)
}

type Recorder interface {
	SaveCheckRun(ctx context.Context, domainID uuid.UUID, cs diff.Changeset) error
}

type ApplyRequest struct {
	ApplyUpdates bool
	ApplyPrunes  bool
}

type DomainService struct {
	loader Loader
	rec    Recorder
	reg    *registry.Registry
	cipher *crypto.Cipher
}

func New(loader Loader, rec Recorder, reg *registry.Registry, cipher *crypto.Cipher) *DomainService {
	return &DomainService{loader: loader, rec: rec, reg: reg, cipher: cipher}
}

// resolve loads the domain, its provider and decrypted credentials, and computes the diff.
// projectID scopes the lookup so a domainID belonging to another tenant's
// project can never be resolved here (closes IDOR).
func (s *DomainService) resolve(ctx context.Context, projectID, domainID uuid.UUID) (provider.Provider, provider.Credentials, DomainRef, diff.Changeset, error) {
	ref, err := s.loader.LoadDomain(ctx, projectID, domainID)
	if err != nil {
		return nil, provider.Credentials{}, ref, diff.Changeset{}, err
	}
	p, err := s.reg.ByName(ref.Provider)
	if err != nil {
		return nil, provider.Credentials{}, ref, diff.Changeset{}, err
	}
	secret, err := s.cipher.Decrypt(ref.SecretEnc)
	if err != nil {
		return nil, provider.Credentials{}, ref, diff.Changeset{}, err
	}
	creds := provider.Credentials{Secret: string(secret)}
	actual, err := p.GetRecords(ctx, creds, ref.ZoneID)
	if err != nil {
		return nil, provider.Credentials{}, ref, diff.Changeset{}, err
	}
	cs := diff.Diff(ref.Template.ToModel(), actual)
	return p, creds, ref, cs, nil
}

// Check computes and records the diff between template and zone.
func (s *DomainService) Check(ctx context.Context, projectID, domainID uuid.UUID) (diff.Changeset, error) {
	_, _, _, cs, err := s.resolve(ctx, projectID, domainID)
	if err != nil {
		return diff.Changeset{}, err
	}
	if err := s.rec.SaveCheckRun(ctx, domainID, cs); err != nil {
		return diff.Changeset{}, err
	}
	return cs, nil
}

// Apply applies updates always (when ApplyUpdates) and prunes only when ApplyPrunes.
func (s *DomainService) Apply(ctx context.Context, projectID, domainID uuid.UUID, req ApplyRequest) (diff.Changeset, error) {
	p, creds, ref, cs, err := s.resolve(ctx, projectID, domainID)
	if err != nil {
		return diff.Changeset{}, err
	}
	var toApply []diff.RecordDiff
	if req.ApplyUpdates {
		toApply = append(toApply, cs.Updates()...)
	}
	if req.ApplyPrunes {
		toApply = append(toApply, cs.Prunes()...)
	}
	applied := diff.Changeset{Diffs: toApply}
	if len(toApply) > 0 {
		if err := p.ApplyChanges(ctx, creds, ref.ZoneID, applied); err != nil {
			return diff.Changeset{}, err
		}
	}
	return applied, nil
}