package service

import (
	"bufio"
	"encoding/json"
	"strings"
	"time"
)

const progressLogPrefix = "METIS_PROGRESS "

// RemoteProgressUpdate is emitted by remote workers so the UI can show
// concrete stage transitions instead of relying only on elapsed-time guesses.
type RemoteProgressUpdate struct {
	Stage        string  `json:"stage,omitempty"`
	ProgressPct  float64 `json:"progress_pct,omitempty"`
	Message      string  `json:"message,omitempty"`
	WrittenBytes int64   `json:"written_bytes,omitempty"`
	TotalBytes   int64   `json:"total_bytes,omitempty"`
}

// ProgressLogLine formats a progress update for remote worker stdout.
func ProgressLogLine(update RemoteProgressUpdate) string {
	data, err := json.Marshal(update)
	if err != nil {
		return ""
	}
	return progressLogPrefix + string(data)
}

func parseRemoteProgressLogs(logs string) (RemoteProgressUpdate, bool) {
	scanner := bufio.NewScanner(strings.NewReader(logs))
	scanner.Buffer(make([]byte, 0, 4096), 1<<20)
	var latest RemoteProgressUpdate
	found := false
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if !strings.HasPrefix(line, progressLogPrefix) {
			continue
		}
		raw := strings.TrimSpace(strings.TrimPrefix(line, progressLogPrefix))
		var update RemoteProgressUpdate
		if err := json.Unmarshal([]byte(raw), &update); err != nil {
			continue
		}
		latest = update
		found = true
	}
	return latest, found
}

func (a *App) applyRemoteProgress(jobID string, update RemoteProgressUpdate) {
	if strings.TrimSpace(jobID) == "" {
		return
	}
	a.setJob(jobID, func(j *Job) {
		if j == nil || j.Status != JobRunning {
			return
		}
		if stage := strings.TrimSpace(update.Stage); stage != "" && stage != j.Stage {
			j.Stage = stage
			j.StageStartedAt = time.Now().UTC()
		}
		if update.ProgressPct > j.ProgressPct {
			j.ProgressPct = update.ProgressPct
		}
		if message := strings.TrimSpace(update.Message); message != "" {
			j.Message = message
		}
		if update.WrittenBytes > 0 {
			j.Written = update.WrittenBytes
		}
		if update.TotalBytes > 0 {
			j.Total = update.TotalBytes
		}
	})
}