package ai

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

// Verdict is the drift judge's call on a single window.
type Verdict struct {
	OnTask bool
	Reason string
}

// ErrInvalidVerdict marks a parseable-but-unusable judge response.
var ErrInvalidVerdict = errors.New("ai: invalid verdict")

type rawVerdict struct {
	OnTask bool   `json:"on_task"`
	Reason string `json:"reason"`
}

// parseVerdict extracts and validates a Verdict from raw CLI output. It reuses
// extractJSON and the shared empty/no-JSON sentinels. A drifting verdict with no
// reason is unusable for the UI and is rejected as ErrInvalidVerdict.
func parseVerdict(s string) (Verdict, error) {
	if strings.TrimSpace(s) == "" {
		return Verdict{}, ErrEmptyResponse
	}
	if strings.IndexByte(s, '{') < 0 {
		return Verdict{}, ErrNoJSON
	}
	jsonStr, err := extractJSON(s)
	if err != nil {
		return Verdict{}, fmt.Errorf("%w: %v", ErrInvalidVerdict, err)
	}
	var raw rawVerdict
	if err := json.Unmarshal([]byte(jsonStr), &raw); err != nil {
		return Verdict{}, fmt.Errorf("%w: %v", ErrInvalidVerdict, err)
	}
	v := Verdict{OnTask: raw.OnTask, Reason: strings.TrimSpace(raw.Reason)}
	if !v.OnTask && v.Reason == "" {
		return Verdict{}, ErrInvalidVerdict
	}
	return v, nil
}