package proposals

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

// ReplacementPolicy controls how original_text spans are replaced in a target segment.
type ReplacementPolicy string

const (
	ReplacementPolicyRequireUnique ReplacementPolicy = "require_unique"
	ReplacementPolicyReplaceAll    ReplacementPolicy = "replace_all"
)

func (p ReplacementPolicy) IsValid() bool {
	switch p {
	case ReplacementPolicyRequireUnique, ReplacementPolicyReplaceAll:
		return true
	default:
		return false
	}
}

func ParseReplacementPolicy(raw string) (ReplacementPolicy, error) {
	parsed := ReplacementPolicy(strings.TrimSpace(raw))
	if !parsed.IsValid() {
		return "", fmt.Errorf("replacement policy must be one of: require_unique, replace_all")
	}
	return parsed, nil
}

func (p *ReplacementPolicy) UnmarshalJSON(data []byte) error {
	var raw string
	if err := json.Unmarshal(data, &raw); err != nil {
		return fmt.Errorf("replacement policy must be a JSON string: %w", err)
	}

	parsed, err := ParseReplacementPolicy(raw)
	if err != nil {
		return err
	}

	*p = parsed
	return nil
}