package tui

import (
	"errors"
	"strings"

	"github.com/atotto/clipboard"
	tea "github.com/charmbracelet/bubbletea"

	"codey/internal/attach"
)

// Pasting a picture into a terminal is not one gesture but three, because no
// terminal sends image bytes to the program inside it:
//
//   - ctrl-V reaches here on terminals that do not eat it (most Linux ones,
//     where the paste key is ctrl-shift-V). The clipboard is then read
//     directly, behind the keystroke.
//   - A terminal that does eat ctrl-V pastes the clipboard's text form, which
//     for a screenshot is nothing at all. An empty paste is therefore taken as
//     a paste attempt too, and answered the same way.
//   - Dragging a file in, or copying one in a file manager, pastes its path.
//     A path ending in an image extension that is really on disk is read.
//
// What goes in the prompt box is [image 1]. The picture travels beside the
// text, and the marker is where it will sit in the message.

// imageMsg carries the result of a clipboard grab back to the UI. quiet marks
// the attempts that were only a guess — an empty paste, which is usually just
// an empty clipboard — so a miss passes without a word. text is the clipboard's
// words, fetched only when a miss should fall back to pasting them.
type imageMsg struct {
	im    attach.Image
	text  string
	err   error
	quiet bool
}

// grabImage reads the clipboard off the UI goroutine. The helpers it shells
// out to can take a moment, and a prompt box that stops taking keys while the
// clipboard is consulted would be worse than no feature.
//
// withText asks for the clipboard's text as well, for the case where there is
// no picture on it. That is the fallback behind ctrl-V: the key means paste,
// and it should paste whatever is there.
func (m *model) grabImage(quiet, withText bool) tea.Cmd {
	grab := m.grabFn
	if grab == nil {
		grab = attach.Clipboard
	}
	readText := m.textFn
	if readText == nil {
		readText = clipboard.ReadAll
	}
	return func() tea.Msg {
		im, err := grab()
		if err == nil || !withText {
			return imageMsg{im: im, err: err, quiet: quiet}
		}
		// No picture. Whatever words are there are what the key was for.
		text, textErr := readText()
		if textErr != nil || text == "" {
			return imageMsg{err: err, quiet: quiet}
		}
		return imageMsg{text: text, quiet: quiet}
	}
}

// attachImage puts an image on the pending set and its marker in the prompt.
func (m *model) attachImage(im attach.Image) tea.Cmd {
	n := m.imgs.Add(im)
	marker := attach.Marker(n)
	// A marker needs air around it: run into the words on either side it stops
	// looking like one thing.
	if v := m.input.Value(); v != "" && !strings.HasSuffix(v, " ") && !strings.HasSuffix(v, "\n") {
		marker = " " + marker
	}
	m.input.InsertString(marker + " ")
	m.growInput()
	m.copied = "🖼 " + attach.Marker(n) + " attached"
	if im.Origin != "" && im.Origin != "clipboard" {
		m.copied += " from " + truncate(im.Origin, 24)
	}
	return nil
}

// onImage handles a finished grab.
func (m *model) onImage(msg imageMsg) tea.Cmd {
	if msg.text != "" {
		// No picture, but words: ctrl-V doing what it says on terminals that
		// let the key through to us at all.
		m.input.InsertString(msg.text)
		m.growInput()
		m.refreshMenu()
		return nil
	}
	if msg.err != nil {
		if msg.quiet || errors.Is(msg.err, attach.ErrNoImage) {
			// Nothing on the clipboard worth having. The keystroke did what
			// it always did; there is nothing to report.
			return nil
		}
		m.tr.addError("could not paste the image: " + msg.err.Error())
		return m.sync()
	}
	return m.attachImage(msg.im)
}

// onPasteKey looks at a paste before the prompt box gets it, and reports
// whether it took it. Ordinary pasted text is left alone.
func (m *model) onPasteKey(msg tea.KeyMsg) (tea.Cmd, bool) {
	if !msg.Paste {
		return nil, false
	}
	text := string(msg.Runes)
	if strings.TrimSpace(text) == "" {
		// The terminal answered a paste with nothing. Either the clipboard is
		// empty or it holds something with no text form — an image, most
		// likely, which is exactly the case this feature exists for.
		return m.grabImage(true, false), true
	}
	if path, ok := attach.Path(text); ok {
		im, err := attach.FromFile(path)
		if err != nil {
			// A dropped file that cannot be read as an image is still a path
			// somebody meant to put in the box. Say why it did not become a
			// picture, and let the text through as text.
			m.tr.addError("pasted " + truncate(path, 40) + ": " + err.Error())
			return m.sync(), false
		}
		return m.attachImage(im), true
	}
	return nil, false
}

// attachPath answers /image. Typing the path is the way that works on every
// terminal, including the ones that will not pass ctrl-V through and have no
// clipboard helper installed.
func (m *model) attachPath(path string) tea.Cmd {
	path = strings.TrimSpace(path)
	if path == "" {
		// Bare /image means "take what is on the clipboard", which is the
		// same thing ctrl-V does, said out loud.
		return m.grabImage(false, false)
	}
	p, ok := attach.Path(path)
	if !ok {
		m.tr.addError("no image at " + truncate(path, 48) + " — want a png, jpeg, gif or webp that exists")
		return m.sync()
	}
	im, err := attach.FromFile(p)
	if err != nil {
		m.tr.addError(err.Error())
		return m.sync()
	}
	return tea.Batch(m.attachImage(im), m.sync())
}