package staffing

import "errors"

// The module has ONE typed error envelope, used across all four endpoints. The service returns these
// sentinels (or a ValidationError carrying field messages); the handler maps each to a status and a JSON
// body of the shape {"error": {"code", "message", "fields"?}}.
var (
	// ErrNoDatabase: the service has no database configured (503).
	ErrNoDatabase = errors.New("staffing: no database configured")
	// ErrNotFound: the requirement is not a real, open gap in this tenant (404).
	ErrNotFound = errors.New("staffing: requirement not found or not open")
	// ErrConflict: a decision landed on a row that was already decided or concurrently superseded (409).
	ErrConflict = errors.New("staffing: recommendation already decided or superseded")
	// ErrProblemTooLarge and ErrSolveBudget are defined in optimizer.go and map to 413 and 503.
)

// ValidationError carries per field messages for a 422 response (bad parameters: a floor out of range, an
// unknown requirement id in an explicit subset).
type ValidationError struct {
	Fields map[string]string
}

func (e *ValidationError) Error() string { return "staffing: invalid request parameters" }

func validationErr(field, msg string) *ValidationError {
	return &ValidationError{Fields: map[string]string{field: msg}}
}