package operator

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

// OutputFormat selects how runner events are rendered to stdout.
type OutputFormat string

const (
	// OutputText emits grep-friendly key=value lines (the default).
	OutputText OutputFormat = "text"
	// OutputJSONL emits one JSON object per line.
	OutputJSONL OutputFormat = "jsonl"
)

// noCount marks a step event that has no market result count (for example a
// hello handshake or a transport failure).
const noCount = -1

// StepEvent is one machine-readable record describing a single executed step.
type StepEvent struct {
	Scenario     string
	Step         string
	Action       string
	Status       string
	Count        int
	ErrorCode    string
	ErrorMessage string

	// Backtest-specific output fields
	RunID        string
	RunStatus    string
	StartingCash string
	EndingEquity string
	TotalReturn  string
	TradeCount   int
}

// RunSummary is the final record describing a whole scenario run.
type RunSummary struct {
	Scenario string
	Status   string
	Steps    int
	Passed   int
	ExitCode int
}

// Writer renders runner events to an io.Writer in the selected format. stdout
// carries these machine-readable lines; scripts grep them for status keys.
type Writer struct {
	w      io.Writer
	format OutputFormat
}

// NewWriter returns a Writer for the given format, defaulting to text.
func NewWriter(w io.Writer, format OutputFormat) *Writer {
	if format == "" {
		format = OutputText
	}
	return &Writer{w: w, format: format}
}

// WriteStep renders one executed step.
func (o *Writer) WriteStep(ev StepEvent) {
	if o.format == OutputJSONL {
		fields := map[string]any{
			"type":     "step",
			"scenario": ev.Scenario,
			"step":     ev.Step,
			"action":   ev.Action,
			"status":   ev.Status,
		}
		if ev.Count >= 0 {
			fields["count"] = ev.Count
		}
		if ev.ErrorCode != "" {
			fields["error_code"] = ev.ErrorCode
		}
		if ev.ErrorMessage != "" {
			fields["error_message"] = ev.ErrorMessage
		}
		if ev.RunID != "" {
			fields["run_id"] = ev.RunID
		}
		if ev.RunStatus != "" {
			fields["run_status"] = ev.RunStatus
		}
		if ev.StartingCash != "" {
			fields["starting_cash"] = ev.StartingCash
		}
		if ev.EndingEquity != "" {
			fields["ending_equity"] = ev.EndingEquity
		}
		if ev.TotalReturn != "" {
			fields["total_return"] = ev.TotalReturn
		}
		if ev.TradeCount > 0 {
			fields["trade_count"] = ev.TradeCount
		}
		o.writeJSON(fields)
		return
	}

	line := fmt.Sprintf("scenario=%s step=%s action=%s status=%s", ev.Scenario, ev.Step, ev.Action, ev.Status)
	if ev.Count >= 0 {
		line += fmt.Sprintf(" count=%d", ev.Count)
	}
	if ev.ErrorCode != "" {
		line += fmt.Sprintf(" error.code=%s", ev.ErrorCode)
	}
	if ev.ErrorMessage != "" {
		line += fmt.Sprintf(" error.message=%q", ev.ErrorMessage)
	}
	if ev.RunID != "" {
		line += fmt.Sprintf(" run.id=%s", ev.RunID)
	}
	if ev.RunStatus != "" {
		line += fmt.Sprintf(" run.status=%s", ev.RunStatus)
	}
	if ev.StartingCash != "" {
		line += fmt.Sprintf(" starting_cash=%s", ev.StartingCash)
	}
	if ev.EndingEquity != "" {
		line += fmt.Sprintf(" ending_equity=%s", ev.EndingEquity)
	}
	if ev.TotalReturn != "" {
		line += fmt.Sprintf(" total_return=%s", ev.TotalReturn)
	}
	if ev.TradeCount > 0 {
		line += fmt.Sprintf(" trade_count=%d", ev.TradeCount)
	}
	fmt.Fprintln(o.w, line)
}

// WriteSummary renders the final run summary.
func (o *Writer) WriteSummary(s RunSummary) {
	if o.format == OutputJSONL {
		o.writeJSON(map[string]any{
			"type":      "summary",
			"scenario":  s.Scenario,
			"status":    s.Status,
			"steps":     s.Steps,
			"passed":    s.Passed,
			"exit_code": s.ExitCode,
		})
		return
	}
	fmt.Fprintf(o.w, "scenario=%s status=%s steps=%d passed=%d exit_code=%d\n", s.Scenario, s.Status, s.Steps, s.Passed, s.ExitCode)
}

func (o *Writer) writeJSON(fields map[string]any) {
	data, err := json.Marshal(fields)
	if err != nil {
		// Marshalling a map of strings/ints cannot realistically fail; fall back
		// to a minimal line so a step result is never silently dropped.
		fmt.Fprintf(o.w, "{\"type\":\"error\",\"error_message\":%q}\n", err.Error())
		return
	}
	fmt.Fprintln(o.w, string(data))
}