servitor/ui/ui.go

package ui

import (
	"fmt"
	"servitor/ansi"
	"servitor/config"
	"servitor/feed"
	"servitor/history"
	"servitor/mime"
	"servitor/pub"
	"servitor/splicer"
	"servitor/style"
	"os/exec"
	"strconv"
	"strings"
	"sync"
	"errors"
)

/*
	The public methods herein are threadsafe, the private methods
	are not and need to be protected by State.m
*/

/* Modes */
const (
	loading = iota
	normal
	command
	selection
	opening
	problem
)

const (
	enterKey     byte = '\r'
	escapeKey    byte = 27
	backspaceKey byte = 127
)

type Page struct {
	feed *feed.Feed

	frontier  pub.Tangible
	loadingUp bool

	children    pub.Container
	basepoint   uint
	loadingDown bool
}

type State struct {
	m *sync.Mutex

	h history.History[*Page]

	width  int
	height int
	output func(string)

	mode   int
	buffer string
}

func (s *State) view() string {
	const cursor = "┃ "

	const parentConnector = "  │\n"
	const childConnector = "\n"

	if s.mode == loading {
		return ansi.CenterVertically("", style.Color("  Loading…"), "", uint(s.height))
	}

	var top, center, bottom string
	for i := -config.Parsed.Style.Context; i <= config.Parsed.Style.Context; i++ {
		if !s.h.Current().feed.Contains(i) {
			continue
		}
		var serialized string
		if s.h.Current().feed.IsParent(i) {
			serialized = s.h.Current().feed.Get(i).Preview(s.width - 4)
		} else if s.h.Current().feed.IsChild(i) {
			serialized = "→ " + ansi.Indent(s.h.Current().feed.Get(i).Preview(s.width-8), "  ", false)
		} else {
			serialized = s.h.Current().feed.Get(i).String(s.width - 4)
		}
		if i == 0 {
			center = ansi.Indent(serialized, cursor, true)
			if s.h.Current().feed.IsParent(i) {
				bottom = parentConnector
			} else {
				bottom = childConnector
			}
			continue
		}

		serialized = ansi.Indent(serialized, "  ", true) + "\n"
		if s.h.Current().feed.IsParent(i) {
			serialized += parentConnector
		} else {
			serialized += childConnector
		}
		if i < 0 {
			top += serialized
		} else {
			bottom += serialized
		}
	}
	if s.h.Current().loadingUp && !s.h.Current().feed.Contains(-config.Parsed.Style.Context-1) {
		top = "\n  " + style.Color("Loading…") + "\n\n" + top
	}
	if s.h.Current().loadingDown && !s.h.Current().feed.Contains(config.Parsed.Style.Context+1) {
		bottom += "  " + style.Color("Loading…") + "\n"
	}

	/* Remove trailing newlines */
	top = strings.TrimSuffix(top, "\n")
	bottom = strings.TrimSuffix(bottom, "\n")

	output := ansi.CenterVertically(top, center, bottom, uint(s.height))

	var footer string
	switch s.mode {
	case normal:
		break
	case selection:
		footer = "Selecting " + s.buffer + " (press . to open internally, enter to open externally)"
	case command:
		footer = ":" + s.buffer
	case opening:
		footer = "Opening " + s.buffer + "\u2026"
	case problem:
		footer = s.buffer
	default:
		panic("encountered unrecognized mode")
	}
	if footer != "" {
		output = ansi.ReplaceLastLine(output, style.Highlight(ansi.SetLength(footer, s.width, "\u2026")))
	}

	return output
}

func (s *State) Update(input byte) {
	s.m.Lock()
	defer s.m.Unlock()

	if s.mode == loading {
		return
	}

	if input == escapeKey {
		s.buffer = ""
		s.mode = normal
		s.output(s.view())
		return
	}

	if input == backspaceKey {
		if len(s.buffer) == 0 {
			s.mode = normal
			s.output(s.view())
			return
		}
		bufferRunes := []rune(s.buffer)
		s.buffer = string(bufferRunes[:len(bufferRunes)-1])
		if s.buffer == "" && s.mode == selection {
			s.mode = normal
		}
		s.output(s.view())
		return
	}

	if s.mode == command {
		if input == enterKey {
			if args := strings.SplitN(s.buffer, " ", 2); len(args) == 2 {
				err := s.subcommand(args[0], args[1])
				if err != nil {
					s.buffer = "Failed to run command: " + err.Error()
					s.mode = problem
					s.output(s.view())
					s.buffer = ""
					s.mode = normal
				}
			} else {
				s.buffer = ""
				s.mode = normal
				s.output(s.view())
			}
			return
		}
		s.buffer += string(input)
		s.output(s.view())
		return
	}

	if input == ':' {
		s.buffer = ""
		s.mode = command
		s.output(s.view())
		return
	}

	if input >= '0' && input <= '9' {
		if s.mode != selection {
			s.buffer = ""
		}
		s.buffer += string(input)
		s.mode = selection
		s.output(s.view())
		return
	}

	if s.mode == selection {
		if input == '.' || input == enterKey {
			number, err := strconv.Atoi(s.buffer)
			if err != nil {
				panic("buffer had a non-number while in selection mode")
			}
			link, mediaType, present := s.h.Current().feed.Current().SelectLink(number)
			if !present {
				s.buffer = ""
				s.mode = normal
				s.output(s.view())
				return
			}
			if input == '.' {
				s.openInternally(link)
				return
			}
			if input == enterKey {
				s.openExternally(link, mediaType)
				return
			}

		}
		/* At this point we know input is a non-number, non-., non-enter */
		s.mode = normal
		s.buffer = ""
	}

	if s.mode == opening {
		s.mode = normal
		s.buffer = ""
	}

	/* At this point we know we are in normal mode */
	switch input {
	case 'k': // up
		s.h.Current().feed.MoveUp()
		s.loadSurroundings()
	case 'j': // down
		s.h.Current().feed.MoveDown()
		s.loadSurroundings()
	case 'g': // return to OP
		s.h.Current().feed.MoveToCenter()
	case 'h': // back in history
		s.h.Back()
	case 'l': // forward in history
		s.h.Forward()
	case ' ': // select
		s.switchTo(s.h.Current().feed.Current())
	case 'c': // get creator of post
		unwrapped := s.h.Current().feed.Current()
		if activity, ok := unwrapped.(*pub.Activity); ok {
			unwrapped = activity.Target()
		}
		if post, ok := unwrapped.(*pub.Post); ok {
			creators := post.Creators()
			s.switchTo(creators)
		}
	case 'r': // get recipient of post
		unwrapped := s.h.Current().feed.Current()
		if activity, ok := unwrapped.(*pub.Activity); ok {
			unwrapped = activity.Target()
		}
		if post, ok := unwrapped.(*pub.Post); ok {
			recipients := post.Recipients()
			s.switchTo(recipients)
		}
	case 'a': // get actor of activity
		if activity, ok := s.h.Current().feed.Current().(*pub.Activity); ok {
			actor := activity.Actor()
			s.switchTo(actor)
		}
	case 'o':
		unwrapped := s.h.Current().feed.Current()
		if activity, ok := unwrapped.(*pub.Activity); ok {
			unwrapped = activity.Target()
		}
		if post, ok := unwrapped.(*pub.Post); ok {
			if link, mediaType, present := post.Media(); present {
				s.openExternally(link, mediaType)
			}
		}
	case 'p':
		if actor, ok := s.h.Current().feed.Current().(*pub.Actor); ok {
			if link, mediaType, present := actor.ProfilePic(); present {
				s.openExternally(link, mediaType)
			}
		}
	case 'b':
		if actor, ok := s.h.Current().feed.Current().(*pub.Actor); ok {
			if link, mediaType, present := actor.Banner(); present {
				s.openExternally(link, mediaType)
			}
		}
	}
	s.output(s.view())
}

func (s *State) switchTo(item any) {
	switch narrowed := item.(type) {
	case []pub.Tangible:
		if len(narrowed) == 0 {
			return
		}
		if len(narrowed) == 1 {
			s.h.Add(&Page{
				feed:     feed.Create(narrowed[0]),
				children: narrowed[0].Children(),
				frontier: narrowed[0],
			})
		} else {
			s.h.Add(&Page{
				feed: feed.CreateAndAppend(narrowed),
			})
		}
	case pub.Tangible:
		s.h.Add(&Page{
			feed:     feed.Create(narrowed),
			children: narrowed.Children(),
			frontier: narrowed,
		})
	case pub.Container:
		if s.mode != loading {
			s.mode = loading
			s.buffer = ""
			s.output(s.view())
		}
		children, nextCollection, newBasepoint := narrowed.Harvest(uint(config.Parsed.Style.Context + 1), 0)
		s.h.Add(&Page{
			basepoint: newBasepoint,
			children:  nextCollection,
			feed:      feed.CreateAndAppend(children),
		})
	default:
		panic("can't switch to non-Tangible non-Container")
	}
	s.mode = normal
	s.buffer = ""
	s.loadSurroundings()
}

func (s *State) SetWidthHeight(width int, height int) {
	s.m.Lock()
	defer s.m.Unlock()
	if s.width == width && s.height == height {
		return
	}
	s.width = width
	s.height = height
	s.output(s.view())
}

func (s *State) loadSurroundings() {
	page := s.h.Current()
	context := config.Parsed.Style.Context
	if !page.loadingUp && !page.feed.Contains(-context) && page.frontier != nil {
		page.loadingUp = true
		go func() {
			parents, newFrontier := page.frontier.Parents(uint(context))
			s.m.Lock()
			page.feed.Prepend(parents)
			page.frontier = newFrontier
			page.loadingUp = false
			s.output(s.view())
			s.m.Unlock()
		}()
	}
	if !page.loadingDown && !page.feed.Contains(context) && page.children != nil {
		page.loadingDown = true
		go func() {
			// TODO: need to do a new renaming, maybe upperFrontier, lowerFrontier
			children, nextCollection, newBasepoint := page.children.Harvest(uint(context), page.basepoint)
			s.m.Lock()
			page.feed.Append(children)
			page.children = nextCollection
			page.basepoint = newBasepoint
			page.loadingDown = false
			s.output(s.view())
			s.m.Unlock()
		}()
	}
}

func (s *State) openUserInput(input string) {
	s.mode = loading
	s.buffer = ""
	s.output(s.view())
	go func() {
		result := pub.FetchUserInput(input)
		s.m.Lock()
		s.switchTo(result)
		s.output(s.view())
		s.m.Unlock()
	}()
}

func (s *State) openInternally(input string) {
	s.mode = loading
	s.buffer = ""
	s.output(s.view())
	go func() {
		result := pub.New(input, nil)
		s.m.Lock()
		s.switchTo(result)
		s.output(s.view())
		s.m.Unlock()
	}()
}

func (s *State) openFeed(input string) {
	inputs, present := config.Parsed.Feeds[input]
	if !present {
		s.mode = problem
		s.buffer = "Failed to open feed: " + input + " is not a known feed"
		s.output(s.view())
		s.mode = normal
		s.buffer = ""
		return
	}
	s.mode = loading
	s.buffer = ""
	s.output(s.view())
	go func() {
		result := splicer.NewSplicer(inputs)
		s.switchTo(result)
		s.output(s.view())
	}()
}

func NewState(width int, height int, output func(string)) *State {
	s := &State{
		h:      history.History[*Page]{},
		width:  width,
		height: height,
		output: output,
		m:      &sync.Mutex{},
		mode:   loading,
	}
	return s
}

func (s *State) Subcommand(name, argument string) error {
	s.m.Lock()
	if name == "feed" {
		if _, present := config.Parsed.Feeds[argument]; !present {
			return errors.New("failed to open feed: " + argument + " is not a known feed")
		}
	}
	err := s.subcommand(name, argument)
	if err != nil {
		/* Here I hold the lock indefinitely intentionally, to stop the ui thread and allow main.go to do cleanup */
		return err
	}
	s.m.Unlock()
	return nil
}

func (s *State) subcommand(name, argument string) error {
	switch name {
	case "open":
		s.openUserInput(argument)
	case "feed":
		s.openFeed(argument)
	default:
		return fmt.Errorf("unrecognized subcommand: %s", name)
	}
	return nil
}

func (s *State) openExternally(link string, mediaType *mime.MediaType) {
	s.mode = opening
	s.buffer = link
	s.output(s.view())

	command := make([]string, len(config.Parsed.Media.Hook))
	copy(command, config.Parsed.Media.Hook)

	foundPercentU := false
	for i, field := range command {
		if i == 0 {
			continue
		}
		switch field {
		case "%url":
			command[i] = link
			foundPercentU = true
		case "%mimetype":
			command[i] = mediaType.Essence
		case "%subtype":
			command[i] = mediaType.Subtype
		case "%supertype":
			command[i] = mediaType.Supertype
		}
	}

	cmd := exec.Command(command[0], command[1:]...)
	if !foundPercentU {
		cmd.Stdin = strings.NewReader(link)
	}

	go func() {
		outputBytes, err := cmd.CombinedOutput()
		output := string(outputBytes)

		s.m.Lock()
		defer s.m.Unlock()

		if s.mode != opening {
			return
		}

		if err != nil {
			s.mode = problem
			s.buffer = "Failed to open link: " + output
			s.output(s.view())
			s.mode = normal
			s.buffer = ""
			return
		}

		s.mode = normal
		s.buffer = ""
		s.output(s.view())
	}()
}