/**
 * @file AgentInstructionsSettings — Settings → AI tools → My agent
 * instructions (issue #67): the account's own rules in markdown, put before
 * every workspace's own instructions in each new Claude or Codex session of a
 * workspace it owns (`GET/PUT /api/me/instructions`). Saved per account. A
 * failed load says so with a Retry instead of leaving a dead, empty editor —
 * the editor stays read-only until the saved text is known, so a save can
 * never overwrite instructions it did not load. **Choose file** reads a local
 * Markdown/text file in the browser into the draft (nothing is uploaded until
 * Save, and Discard brings the saved text back). "Applies to" lists only the
 * installed, enabled tools whose panes the server says receive them.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

import { useEffect, useRef, useState, type ChangeEvent } from "react";
import { FileUp } from "lucide-react";
import { useTranslation } from "react-i18next";
import { api, type AgentInstructionsView } from "../../lib/api";
import { useAiTools } from "../../hooks/useAiTools";
import { AiToolIcon } from "../AiToolIcon";
import { toast } from "../../lib/toast";
import { SettingsSection } from "./SettingsRow";

export function AgentInstructionsSettings() {
  const { t } = useTranslation("settings");
  const [saved, setSaved] = useState<string | null>(null);
  const [draft, setDraft] = useState("");
  const [max, setMax] = useState<number | undefined>();
  const [toolIds, setToolIds] = useState<string[]>([]);
  const { tools } = useAiTools();
  const [loadError, setLoadError] = useState<string | null>(null);
  const [saving, setSaving] = useState(false);
  const fileInput = useRef<HTMLInputElement | null>(null);

  const apply = (r: AgentInstructionsView) => {
    setSaved(r.instructions);
    setDraft(r.instructions);
    setMax(r.max);
    setToolIds(r.tools ?? []);
  };

  const load = () => {
    setLoadError(null);
    api.me
      .instructions()
      .then(apply)
      .catch((err) => setLoadError(err instanceof Error ? err.message : String(err)));
  };

  useEffect(load, []);

  async function save() {
    setSaving(true);
    try {
      apply(await api.me.saveInstructions(draft));
      toast.success(t("agentInstructions.saved"));
    } catch (err) {
      toast.error(
        t("agentInstructions.saveFailed", { message: err instanceof Error ? err.message : "" })
      );
    } finally {
      setSaving(false);
    }
  }

  async function pickFile(e: ChangeEvent<HTMLInputElement>) {
    const file = e.target.files?.[0];
    e.target.value = ""; // the same file can be picked again after a Discard
    if (!file) return;
    const text = await file.text();
    if (max && text.length > max) {
      toast.error(
        t("agentInstructions.fileTooBig", {
          name: file.name,
          size: text.length.toLocaleString(),
          max: max.toLocaleString(),
        })
      );
      return;
    }
    setDraft(text);
  }

  const appliesTo = tools.filter((x) => x.installed && x.enabled && toolIds.includes(x.id));
  const ready = saved !== null;
  const dirty = ready && draft !== saved;

  return (
    <SettingsSection
      id="agent-instructions"
      title={t("agentInstructions.title")}
      description={t("agentInstructions.description")}
    >
      <div className="pt-1">
        {appliesTo.length > 0 && (
          <div className="mb-3 flex flex-wrap items-center gap-1.5 text-xs text-fg-muted">
            <span>{t("agentInstructions.appliesTo")}</span>
            {appliesTo.map((x) => (
              <span
                key={x.id}
                className="inline-flex items-center gap-1.5 rounded-full border border-border bg-surface-2 py-0.5 pl-1 pr-2.5 text-fg-secondary"
              >
                <AiToolIcon tool={x} className="h-4 w-4" />
                {x.label}
              </span>
            ))}
          </div>
        )}
        <textarea
          aria-label={t("agentInstructions.title")}
          className="block w-full min-h-[180px] resize-y rounded-lg border border-border bg-surface-1 px-3 py-2.5 font-mono text-xs leading-relaxed text-fg-primary placeholder:text-fg-muted/70 focus:border-accent focus:outline-none disabled:opacity-60"
          rows={8}
          spellCheck={false}
          placeholder={t("agentInstructions.placeholder")}
          value={draft}
          maxLength={max}
          disabled={!ready}
          onChange={(e) => setDraft(e.target.value)}
        />
        <div className="mt-3 flex items-center justify-between gap-3">
          {loadError ? (
            <p className="flex min-w-0 items-center gap-2 text-xs text-status-danger">
              <span className="truncate">
                {t("agentInstructions.loadFailed", { message: loadError })}
              </span>
              <button type="button" className="btn-ghost shrink-0 text-xs" onClick={load}>
                {t("common:retry")}
              </button>
            </p>
          ) : (
            <span className="text-[11px] tabular-nums text-fg-muted">
              {ready && max ? `${draft.length.toLocaleString()} / ${max.toLocaleString()}` : ""}
            </span>
          )}
          <div className="flex shrink-0 items-center gap-2">
            <input
              ref={fileInput}
              type="file"
              accept=".md,.markdown,.txt,text/markdown,text/plain"
              className="hidden"
              data-testid="agent-instructions-file"
              onChange={(e) => void pickFile(e)}
            />
            <button
              type="button"
              className="btn-ghost inline-flex items-center gap-1.5 text-xs disabled:opacity-50"
              disabled={!ready || saving}
              onClick={() => fileInput.current?.click()}
            >
              <FileUp className="h-3.5 w-3.5" />
              {t("agentInstructions.chooseFile")}
            </button>
            {dirty && !saving && (
              <button type="button" className="btn-ghost text-xs" onClick={() => setDraft(saved)}>
                {t("agentInstructions.discard")}
              </button>
            )}
            <button
              type="button"
              className="btn-primary text-xs disabled:cursor-not-allowed disabled:opacity-50"
              disabled={saving || !dirty}
              onClick={() => void save()}
            >
              {saving ? t("homeDir.saving") : t("homeDir.save")}
            </button>
          </div>
        </div>
      </div>
    </SettingsSection>
  );
}