package app

import (
	"context"

	"rickub.com/turbo-editors/turbo-core/lsp"
)

// RequestCompletion asks the language server what could be typed here and
// opens the popup with the answer.
//
// It is deliberately synchronous: the request has its own short timeout, and a
// completion that arrives after the user has typed three more characters is
// worse than none at all.
func (a *App) RequestCompletion() {
	view := a.activeView()
	if view == nil {
		return
	}
	if !a.language.Ready() {
		a.Message(a.language.Status())
		return
	}

	buf := view.Buffer()
	cursor := buf.Cursor()

	items, err := a.language.Complete(context.Background(),
		buf.Path(), cursor.Line, cursor.Col, buf.Line(cursor.Line))
	if err != nil {
		a.Message("Completion: " + err.Error())
		return
	}
	if len(items) == 0 {
		a.Message(a.noCompletionsReason(buf.Path()))
		return
	}

	x, y := view.CursorScreenPosition()
	a.completion.Show(items, view.WordBeforeCursor(), x, y, a.screenRect())
}

// refreshCompletionPrefix narrows the open popup as the user keeps typing.
func (a *App) refreshCompletionPrefix() {
	if !a.completion.Visible() {
		return
	}
	if view := a.activeView(); view != nil {
		a.completion.SetPrefix(view.WordBeforeCursor())
	}
}

// acceptCompletion puts the chosen suggestion into the buffer, replacing the
// part of the word that had already been typed.
func (a *App) acceptCompletion(item lsp.CompletionItem) {
	if view := a.activeView(); view != nil {
		view.ReplaceWordBeforeCursor(item.Insertion())
	}
}

// noCompletionsReason explains an empty completion list.
//
// A language server answers nothing at all — no error, just an empty list —
// for a package it cannot load, which is what a duplicate declaration or an
// unresolved import produces. Saying "no completions" and stopping there
// leaves the user with nowhere to go, when the server has already said what is
// wrong through its diagnostics.
func (a *App) noCompletionsReason(path string) string {
	if diagnostic, ok := a.language.FirstError(path); ok {
		return "No completions — this file does not compile: " + diagnostic.Message
	}
	return "No completions here"
}