package customer

import (
	"encoding/json"
	"fmt"
	"strings"
)

type companySelectionObject struct {
	ID string `json:"id"`
}

// decodeCompanySelection parses company IDs sent as strings, legacy company_ids,
// or company summary objects returned by GET customer.
func decodeCompanySelection(raw json.RawMessage) ([]string, error) {
	if len(raw) == 0 {
		return nil, fmt.Errorf("empty company selection")
	}
	if string(raw) == "null" {
		return []string{}, nil
	}

	var ids []string
	if err := json.Unmarshal(raw, &ids); err == nil {
		return ids, nil
	}

	var objects []companySelectionObject
	if err := json.Unmarshal(raw, &objects); err == nil {
		result := make([]string, 0, len(objects))
		for _, object := range objects {
			if id := strings.TrimSpace(object.ID); id != "" {
				result = append(result, id)
			}
		}
		return result, nil
	}

	return nil, fmt.Errorf("companies must be an array of IDs or objects with id")
}

func mergeCompanySelectionFields(raw map[string]json.RawMessage) (json.RawMessage, bool, error) {
	if value, ok := raw["companies"]; ok {
		return value, true, nil
	}
	if value, ok := raw["company_ids"]; ok {
		return value, true, nil
	}
	return nil, false, nil
}

func unmarshalFormWithoutCompanyFields(data []byte, raw map[string]json.RawMessage, target any) error {
	delete(raw, "companies")
	delete(raw, "company_ids")

	trimmed, err := json.Marshal(raw)
	if err != nil {
		return err
	}

	return json.Unmarshal(trimmed, target)
}

// UnmarshalJSON accepts companies, legacy company_ids, and company summary objects.
func (f *CreateCustomerForm) UnmarshalJSON(data []byte) error {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(data, &raw); err != nil {
		return err
	}

	selectionRaw, present, err := mergeCompanySelectionFields(raw)
	if err != nil {
		return err
	}

	type alias CreateCustomerForm
	if err := unmarshalFormWithoutCompanyFields(data, raw, (*alias)(f)); err != nil {
		return err
	}

	if !present {
		return nil
	}

	companies, err := decodeCompanySelection(selectionRaw)
	if err != nil {
		return err
	}
	f.Companies = companies

	return nil
}

// UnmarshalJSON accepts companies, legacy company_ids, and company summary objects.
func (f *UpdateCustomerForm) UnmarshalJSON(data []byte) error {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(data, &raw); err != nil {
		return err
	}

	selectionRaw, present, err := mergeCompanySelectionFields(raw)
	if err != nil {
		return err
	}

	type alias UpdateCustomerForm
	if err := unmarshalFormWithoutCompanyFields(data, raw, (*alias)(f)); err != nil {
		return err
	}

	if !present {
		return nil
	}

	companies, err := decodeCompanySelection(selectionRaw)
	if err != nil {
		return err
	}
	f.Companies = &companies

	return nil
}

// UnmarshalJSON accepts companies, legacy company_ids, and company summary objects.
func (f *AssignCompaniesForm) UnmarshalJSON(data []byte) error {
	var raw map[string]json.RawMessage
	if err := json.Unmarshal(data, &raw); err != nil {
		return err
	}

	selectionRaw, present, err := mergeCompanySelectionFields(raw)
	if err != nil {
		return err
	}

	type alias AssignCompaniesForm
	if err := unmarshalFormWithoutCompanyFields(data, raw, (*alias)(f)); err != nil {
		return err
	}

	if !present {
		return nil
	}

	companies, err := decodeCompanySelection(selectionRaw)
	if err != nil {
		return err
	}
	f.Companies = companies

	return nil
}