package jsonmessage

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"iter"
	"strings"
	"time"

	"github.com/docker/go-units"
	"github.com/moby/moby/api/types/jsonstream"
	"github.com/moby/term"
)

// RFC3339NanoFixed is time.RFC3339Nano with nanoseconds padded using zeros to
// ensure the formatted time isalways the same number of characters.
const RFC3339NanoFixed = "2006-01-02T15:04:05.000000000Z07:00"

// JSONProgress describes a progress message in a JSON stream.
type JSONProgress struct {
	jsonstream.Progress

	// terminalFd is the fd of the current terminal, if any. It is used
	// to get the terminal width.
	terminalFd uintptr

	// nowFunc is used to override the current time in tests.
	nowFunc func() time.Time

	// winSize is used to override the terminal width in tests.
	winSize int
}

func (p *JSONProgress) String() string {
	var (
		width      = p.width()
		pbBox      string
		numbersBox string
	)
	if p.Current <= 0 && p.Total <= 0 {
		return ""
	}
	if p.Total <= 0 {
		switch p.Units {
		case "":
			return fmt.Sprintf("%8v", units.HumanSize(float64(p.Current)))
		default:
			return fmt.Sprintf("%d %s", p.Current, p.Units)
		}
	}

	percentage := int(float64(p.Current)/float64(p.Total)*100) / 2
	if percentage > 50 {
		percentage = 50
	}
	if width > 110 {
		// this number can't be negative gh#7136
		numSpaces := 0
		if 50-percentage > 0 {
			numSpaces = 50 - percentage
		}
		pbBox = fmt.Sprintf("[%s>%s] ", strings.Repeat("=", percentage), strings.Repeat(" ", numSpaces))
	}

	switch {
	case p.HideCounts:
	case p.Units == "": // no units, use bytes
		current := units.HumanSize(float64(p.Current))
		total := units.HumanSize(float64(p.Total))

		numbersBox = fmt.Sprintf("%8v/%v", current, total)

		if p.Current > p.Total {
			// remove total display if the reported current is wonky.
			numbersBox = fmt.Sprintf("%8v", current)
		}
	default:
		numbersBox = fmt.Sprintf("%d/%d %s", p.Current, p.Total, p.Units)

		if p.Current > p.Total {
			// remove total display if the reported current is wonky.
			numbersBox = fmt.Sprintf("%d %s", p.Current, p.Units)
		}
	}

	// Show approximation of remaining time if there's enough width.
	var timeLeftBox string
	if width > 50 {
		if p.Current > 0 && p.Start > 0 && percentage < 50 {
			fromStart := p.now().Sub(time.Unix(p.Start, 0))
			perEntry := fromStart / time.Duration(p.Current)
			left := time.Duration(p.Total-p.Current) * perEntry
			timeLeftBox = " " + left.Round(time.Second).String()
		}
	}
	return pbBox + numbersBox + timeLeftBox
}

// now returns the current time in UTC, but can be overridden in tests
// by setting JSONProgress.nowFunc to a custom function.
func (p *JSONProgress) now() time.Time {
	if p.nowFunc != nil {
		return p.nowFunc()
	}
	return time.Now().UTC()
}

// width returns the current terminal's width, but can be overridden
// in tests by setting JSONProgress.winSize to a non-zero value.
func (p *JSONProgress) width() int {
	if p.winSize != 0 {
		return p.winSize
	}
	ws, err := term.GetWinsize(p.terminalFd)
	if err == nil {
		return int(ws.Width)
	}
	return 200
}

// JSONMessage defines a message struct. It describes
// the created time, where it from, status, ID of the
// message. It's used for docker events.
type JSONMessage struct {
	Stream   string            `json:"stream,omitempty"`
	Status   string            `json:"status,omitempty"`
	Progress *JSONProgress     `json:"progressDetail,omitempty"`
	ID       string            `json:"id,omitempty"`
	Error    *jsonstream.Error `json:"errorDetail,omitempty"`
	Aux      *json.RawMessage  `json:"aux,omitempty"` // Aux contains out-of-band data, such as digests for push signing and image id after building.
}

// We can probably use [aec.EmptyBuilder] for managing the output, but
// currently we're doing it all manually, so defining some consts for
// the basics we use.
//
// [aec.EmptyBuilder]: https://pkg.go.dev/github.com/morikuni/aec#EmptyBuilder
const (
	ansiEraseLine     = "\x1b[2K"  // Erase entire line
	ansiCursorUpFmt   = "\x1b[%dA" // Move cursor up N lines
	ansiCursorDownFmt = "\x1b[%dB" // Move cursor down N lines
)

func clearLine(out io.Writer) {
	_, _ = out.Write([]byte(ansiEraseLine))
}

func cursorUp(out io.Writer, l uint) {
	if l == 0 {
		return
	}
	_, _ = fmt.Fprintf(out, ansiCursorUpFmt, l)
}

func cursorDown(out io.Writer, l uint) {
	if l == 0 {
		return
	}
	_, _ = fmt.Fprintf(out, ansiCursorDownFmt, l)
}

// Display prints the JSONMessage to out. If isTerminal is true, it erases
// the entire current line when displaying the progressbar. It returns an
// error if the [JSONMessage.Error] field is non-nil.
func (jm *JSONMessage) Display(out io.Writer, isTerminal bool) error {
	if jm.Error != nil {
		return jm.Error
	}
	var endl string
	if isTerminal && jm.Stream == "" && jm.Progress != nil {
		clearLine(out)
		endl = "\r"
		_, _ = fmt.Fprint(out, endl)
	} else if jm.Progress != nil && jm.Progress.String() != "" { // disable progressbar in non-terminal
		return nil
	}
	if jm.ID != "" {
		_, _ = fmt.Fprintf(out, "%s: ", jm.ID)
	}
	if jm.Progress != nil && isTerminal {
		_, _ = fmt.Fprintf(out, "%s %s%s", jm.Status, jm.Progress.String(), endl)
	} else if jm.Stream != "" {
		_, _ = fmt.Fprintf(out, "%s%s", jm.Stream, endl)
	} else {
		_, _ = fmt.Fprintf(out, "%s%s\n", jm.Status, endl)
	}
	return nil
}

type JSONMessagesStream iter.Seq2[JSONMessage, error]

// DisplayJSONMessagesStream reads a JSON message stream from in, and writes
// each [JSONMessage] to out.
// see DisplayJSONMessages for details
func DisplayJSONMessagesStream(in io.Reader, out io.Writer, terminalFd uintptr, isTerminal bool, auxCallback func(JSONMessage)) error {
	dec := json.NewDecoder(in)
	var f JSONMessagesStream = func(yield func(JSONMessage, error) bool) {
		for {
			var jm JSONMessage
			err := dec.Decode(&jm)
			if errors.Is(err, io.EOF) {
				break
			}
			if !yield(jm, err) {
				return
			}
		}
	}

	return DisplayJSONMessages(f, out, terminalFd, isTerminal, auxCallback)
}

// DisplayJSONMessages writes each [JSONMessage] from stream to out.
// It returns an error if an invalid JSONMessage is received, or if
// a JSONMessage containers a non-zero [JSONMessage.Error].
//
// Presentation of the JSONMessage depends on whether a terminal is attached,
// and on the terminal width. Progress bars ([JSONProgress]) are suppressed
// on narrower terminals (< 110 characters).
//
//   - isTerminal describes if out is a terminal, in which case it prints
//     a newline ("\n") at the end of each line and moves the cursor while
//     displaying.
//   - terminalFd is the fd of the current terminal (if any), and used
//     to get the terminal width.
//   - auxCallback allows handling the [JSONMessage.Aux] field. It is
//     called if a JSONMessage contains an Aux field, in which case
//     DisplayJSONMessagesStream does not present the JSONMessage.
func DisplayJSONMessages(messages JSONMessagesStream, out io.Writer, terminalFd uintptr, isTerminal bool, auxCallback func(JSONMessage)) error {
	ids := make(map[string]uint)

	for jm, err := range messages {
		var diff uint
		if err != nil {
			return err
		}

		if jm.Aux != nil {
			if auxCallback != nil {
				auxCallback(jm)
			}
			continue
		}

		if jm.Progress != nil {
			jm.Progress.terminalFd = terminalFd
		}
		if jm.ID != "" && jm.Progress != nil {
			line, ok := ids[jm.ID]
			if !ok {
				// NOTE: This approach of using len(id) to
				// figure out the number of lines of history
				// only works as long as we clear the history
				// when we output something that's not
				// accounted for in the map, such as a line
				// with no ID.
				line = uint(len(ids))
				ids[jm.ID] = line
				if isTerminal {
					_, _ = fmt.Fprintf(out, "\n")
				}
			}
			diff = uint(len(ids)) - line
			if isTerminal {
				cursorUp(out, diff)
			}
		} else {
			// When outputting something that isn't progress
			// output, clear the history of previous lines. We
			// don't want progress entries from some previous
			// operation to be updated (for example, pull -a
			// with multiple tags).
			ids = make(map[string]uint)
		}
		err := jm.Display(out, isTerminal)
		if jm.ID != "" && isTerminal {
			cursorDown(out, diff)
		}
		if err != nil {
			return err
		}
	}
	return nil
}