package agent

import (
    "fmt"
    "io"
    "os"
    "time"
)

// HeadlessOutput implements the Output interface for non-interactive / pipe mode.
// Text is written to stdout; tool calls, system messages, and errors go to stderr.
type HeadlessOutput struct {
    stdout io.Writer
    stderr io.Writer
}

// NewHeadlessOutput creates a HeadlessOutput that writes text to os.Stdout
// and diagnostics to os.Stderr.
func NewHeadlessOutput() *HeadlessOutput {
    return &HeadlessOutput{
        stdout: os.Stdout,
        stderr: os.Stderr,
    }
}

// newHeadlessOutput creates a HeadlessOutput with custom writers (for testing).
func newHeadlessOutput(stdout, stderr io.Writer) *HeadlessOutput {
    return &HeadlessOutput{
        stdout: stdout,
        stderr: stderr,
    }
}

// StreamText writes incremental text content to stdout.
func (h *HeadlessOutput) StreamText(text string) {
    fmt.Fprint(h.stdout, text)
}

// StreamDone writes a trailing newline to ensure output is terminated.
func (h *HeadlessOutput) StreamDone(evalCount, promptTokens int) {
    fmt.Fprintln(h.stdout)
}

// ToolCallStart writes a brief tool invocation notice to stderr.
func (h *HeadlessOutput) ToolCallStart(name string, args map[string]any) {
    fmt.Fprintf(h.stderr, "→ %s %s\n", name, FormatToolArgs(args))
}

// ToolCallResult writes the tool result summary to stderr.
func (h *HeadlessOutput) ToolCallResult(name string, result string, isError bool, duration time.Duration) {
    status := "ok"
    if isError {
        status = "ERROR"
    }
    // Truncate long results for stderr display.
    display := result
    if len(display) > 200 {
        display = display[:197] + "..."
    }
    fmt.Fprintf(h.stderr, "← %s [%s %s] %s\n", name, status, duration.Round(time.Millisecond), display)
}

// SystemMessage writes a system message to stderr.
func (h *HeadlessOutput) SystemMessage(msg string) {
    fmt.Fprintf(h.stderr, "[system] %s\n", msg)
}

// Error writes an error message to stderr.
func (h *HeadlessOutput) Error(msg string) {
    fmt.Fprintf(h.stderr, "[error] %s\n", msg)
}