// Package ui provides consistent user-facing output formatting for vaultik.
// All status updates, banners, errors, and warnings printed to the user
// should go through a *Writer from this package.
//
// Message classes (see Writer methods):
//
//   - Begin   — operation start, left-aligned, marker "》" (white)
//   - Complete— operation completion, left-aligned, marker "》" (green)
//   - Info    — left-aligned neutral status, marker "》" (white)
//   - Notice  — left-aligned important note, marker "》" (cyan)
//   - Warning — left-aligned warning, full word "Warning: " (orange/yellow)
//   - Error   — left-aligned error, full word "ERROR: " (red)
//   - Progress— indented heartbeat / per-item update, marker "  》" (white)
//   - Banner  — application banner line, left-aligned, no marker
//
// Value formatters (Hex, Size, Duration, Time, Path, Snapshot, Speed,
// Count, Percent) return ANSI-colored strings the caller composes into
// the message body. When color is disabled (non-TTY output or NO_COLOR
// set) all formatters return plain text.
package ui

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

	"github.com/dustin/go-humanize"
	"golang.org/x/term"
)

// ANSI SGR escape sequences.
const (
	ansiReset   = "\033[0m"
	ansiBold    = "\033[1m"
	ansiRed     = "\033[31m"
	ansiGreen   = "\033[32m"
	ansiYellow  = "\033[33m" // used for orange "Warning:" and for durations
	ansiBlue    = "\033[34m"
	ansiMagenta = "\033[35m"
	ansiCyan    = "\033[36m"
	ansiWhite   = "\033[37m"
)

// Marker is the chevron prefix used for all non-error/warning lines.
const Marker = "》"

// Writer formats and emits user-facing messages with optional ANSI color.
type Writer struct {
	out   io.Writer
	color bool
}

// New returns a Writer that emits to out. Color is enabled when out is a
// TTY and the NO_COLOR environment variable is unset.
// https://no-color.org/
func New(out io.Writer) *Writer {
	return &Writer{out: out, color: shouldColor(out)}
}

// NewWithColor returns a Writer with an explicit color setting, ignoring
// TTY detection. Useful for tests and for piped output that the caller
// wants to colorize anyway.
func NewWithColor(out io.Writer, color bool) *Writer {
	return &Writer{out: out, color: color}
}

// Out returns the underlying writer.
func (w *Writer) Out() io.Writer { return w.out }

// Color reports whether color is enabled on this writer.
func (w *Writer) Color() bool { return w.color }

// shouldColor returns true when w is a real TTY and NO_COLOR is unset.
func shouldColor(w io.Writer) bool {
	if os.Getenv("NO_COLOR") != "" {
		return false
	}
	f, ok := w.(*os.File)
	if !ok {
		return false
	}
	return term.IsTerminal(int(f.Fd()))
}

// paint wraps s in the given ANSI color when color is enabled.
func (w *Writer) paint(color, s string) string {
	if !w.color {
		return s
	}
	return color + s + ansiReset
}

// ───────────────────────── message methods ─────────────────────────

// Begin prints an operation-start line, left-aligned with a white marker.
func (w *Writer) Begin(format string, args ...any) {
	w.emit(ansiWhite, Marker, "", format, args)
}

// Complete prints an operation-completion line in green, left-aligned.
func (w *Writer) Complete(format string, args ...any) {
	w.emit(ansiGreen, Marker, ansiGreen, format, args)
}

// Info prints a neutral status line, left-aligned with a white marker.
func (w *Writer) Info(format string, args ...any) {
	w.emit(ansiWhite, Marker, "", format, args)
}

// Notice prints an attention-worthy informational line, marker in cyan.
func (w *Writer) Notice(format string, args ...any) {
	w.emit(ansiCyan, Marker, "", format, args)
}

// Warning prints "⚠️  Warning: " in orange/yellow followed by the message.
func (w *Writer) Warning(format string, args ...any) {
	prefix := "⚠️  " + w.paint(ansiYellow+ansiBold, "Warning: ")
	_, _ = fmt.Fprintln(w.out, prefix+fmt.Sprintf(format, args...))
}

// Error prints "❌ ERROR: " in red followed by the message. Goes to the
// same writer as everything else; callers that want stderr should
// construct a separate Writer for it.
func (w *Writer) Error(format string, args ...any) {
	prefix := "❌ " + w.paint(ansiRed+ansiBold, "ERROR: ")
	_, _ = fmt.Fprintln(w.out, prefix+fmt.Sprintf(format, args...))
}

// Progress prints an indented heartbeat / per-item update, marker in white.
func (w *Writer) Progress(format string, args ...any) {
	w.emit(ansiWhite, "  "+Marker, "", format, args)
}

// Banner prints a line with no marker, left-aligned. Used for the
// application startup banner only.
func (w *Writer) Banner(format string, args ...any) {
	_, _ = fmt.Fprintln(w.out, fmt.Sprintf(format, args...))
}

// emit writes "<prefix> <body>\n" with the prefix painted in prefixColor
// and the body optionally painted in bodyColor (empty = no body color).
func (w *Writer) emit(prefixColor, prefix, bodyColor, format string, args []any) {
	body := fmt.Sprintf(format, args...)
	if bodyColor != "" {
		body = w.paint(bodyColor, body)
	}
	_, _ = fmt.Fprintln(w.out, w.paint(prefixColor, prefix)+" "+body)
}

// ───────────────────────── value formatters ─────────────────────────
//
// These return ANSI-colored strings the caller composes into a message
// body. When color is disabled they return plain text.

// Hex colorizes a hex identifier (blob hash, chunk hash, snapshot id).
// Long hashes are abbreviated to first 12 chars with "...".
func (w *Writer) Hex(s string) string {
	short := s
	if len(s) > 12 {
		short = s[:12] + "..."
	}
	return w.paint(ansiCyan, short)
}

// Snapshot colorizes a snapshot ID (full, no abbreviation).
func (w *Writer) Snapshot(id string) string {
	return w.paint(ansiCyan+ansiBold, id)
}

// Path colorizes a filesystem path.
func (w *Writer) Path(p string) string {
	return w.paint(ansiBlue, p)
}

// Size colorizes a byte count using humanize.Bytes.
func (w *Writer) Size(bytes int64) string {
	return w.paint(ansiMagenta, humanize.Bytes(uint64(bytes)))
}

// Speed colorizes a byte-per-second value as "<size>/sec".
func (w *Writer) Speed(bytesPerSec float64) string {
	return w.paint(ansiMagenta, humanize.Bytes(uint64(bytesPerSec))+"/sec")
}

// Duration colorizes a time.Duration rounded to the nearest second.
func (w *Writer) Duration(d time.Duration) string {
	return w.paint(ansiYellow, d.Round(time.Second).String())
}

// Time colorizes an absolute time (RFC3339, second precision).
func (w *Writer) Time(t time.Time) string {
	return w.paint(ansiYellow, t.Format(time.RFC3339))
}

// Count colorizes an integer count with thousands separators.
func (w *Writer) Count(n int) string {
	return w.paint(ansiMagenta, humanize.Comma(int64(n)))
}

// Percent colorizes a 0..100 percentage.
func (w *Writer) Percent(p float64) string {
	return w.paint(ansiMagenta, fmt.Sprintf("%.1f%%", p))
}