package com.example.aiapp

import android.content.Context
import androidx.core.content.edit

private const val DRAFTS = "session-drafts"

/**
 * A message typed into a session and not sent yet.
 *
 * On this device rather than on the backend, which is where this app otherwise keeps state so that
 * every device sees it. A draft is the case that rule is not about: it is the contents of a text
 * box on the phone somebody is holding, written on every keystroke, and half a sentence surfacing
 * on another device would be a surprise rather than a convenience. What has been *sent* is the
 * server's, and that is the part which has to outlive this phone.
 *
 * Kept per session id, because the thing being typed belongs to the conversation it is aimed at:
 * one shared box would hand a message meant for one session to whichever was opened next.
 */
fun loadDraft(context: Context, sessionId: String): String =
    context.getSharedPreferences(DRAFTS, Context.MODE_PRIVATE).getString(sessionId, "").orEmpty()

/**
 * Records [text] as the draft for [sessionId], or forgets it when there is nothing left to keep.
 *
 * The path out is emptying the box, which is what sending does -- so a sent message removes its own
 * entry and nothing accumulates for a session in ordinary use. A session *deleted* while it held a
 * draft does leave its key behind: pruning those means a pass over the live session list, which
 * this file would otherwise have no reason to know about, and the residue is a few bytes per
 * session ever abandoned mid-sentence. That is a trade rather than an oversight.
 */
fun saveDraft(context: Context, sessionId: String, text: String) {
    context.getSharedPreferences(DRAFTS, Context.MODE_PRIVATE).edit {
        if (text.isEmpty()) remove(sessionId) else putString(sessionId, text)
    }
}