package domain

import (
	"errors"

	contract "git.cin.su/m/Assistant/contracts/situation"
	"git.cin.su/m/Assistant/contracts/work"
)

var (
	ErrNoActiveFocus  = errors.New("no active focus binding")
	ErrStaleFocus     = errors.New("stale focus binding")
	ErrAmbiguousFocus = errors.New("ambiguous focus binding")
	ErrTargetMismatch = errors.New("proposed target does not match resolved focus")
)

// Resolver is a deterministic situation-owned resolver. It accepts runtime
// bindings only; RequestText must never be used to select a project.
type Resolver struct {
	bindings []contract.FocusBinding
}

func NewResolver(bindings []contract.FocusBinding) Resolver {
	return Resolver{bindings: append([]contract.FocusBinding(nil), bindings...)}
}

func (r Resolver) Resolve(runtime contract.RuntimeBinding) (contract.FocusBinding, error) {
	var matches []contract.FocusBinding
	var stale bool
	for _, binding := range r.bindings {
		if binding.SessionID != runtime.SessionID || binding.Workspace != runtime.Workspace {
			continue
		}
		if !binding.Active {
			stale = true
			continue
		}
		matches = append(matches, binding)
	}
	switch len(matches) {
	case 0:
		if stale {
			return contract.FocusBinding{}, ErrStaleFocus
		}
		return contract.FocusBinding{}, ErrNoActiveFocus
	case 1:
		return matches[0], nil
	default:
		return contract.FocusBinding{}, ErrAmbiguousFocus
	}
}

// ValidateTaskTarget prevents cognition from redirecting a request outside the
// resolved situation before a work owner considers its own revision guard.
func ValidateTaskTarget(focus contract.FocusBinding, target work.TaskTarget) error {
	if focus.GoalID != target.GoalID || focus.ScopeID != target.ScopeID {
		return ErrTargetMismatch
	}
	return nil
}