import type { ExtensionAPI, ExtensionCommandContext } from "@earendil-works/pi-coding-agent";

import { resetTemplateReferences } from "../config/update-config.ts";
import { tryResolveGitRepositoryRoot } from "../git/collect-changes.ts";
import { GitClient } from "../git/git-client.ts";
import { listTemplates } from "../templates/list-templates.ts";
import { DEFAULT_TEMPLATE_NAME } from "../templates/load-template.ts";
import { stageUserTemplateRemoval } from "../templates/save-template.ts";

const CANCELLED_MESSAGE = "Cancelled. No template was removed.";

/**
 * 执行 /git-commit remove 的模板删除工作流：
 * 选择或指定用户模板，确认后删除文件，并把仍引用它的配置回退到 default。
 */
export async function runRemoveTemplateFlow(
  pi: ExtensionAPI,
  ctx: ExtensionCommandContext,
): Promise<void> {
  const templates = await listTemplates();
  const userNames = templates
    .filter((template) => template.source === "user")
    .map((template) => template.name);

  if (userNames.length === 0) {
    ctx.ui.notify("No user templates to remove. Built-in templates cannot be removed.", "warning");
    return;
  }
  const name = await ctx.ui.select("Select template to remove", userNames);
  if (name === undefined) {
    ctx.ui.notify(CANCELLED_MESSAGE, "info");
    return;
  }

  const confirmed = await ctx.ui.confirm(
    "Remove template",
    `Delete template "${name}" permanently? This cannot be undone.`,
  );
  if (!confirmed) {
    ctx.ui.notify(CANCELLED_MESSAGE, "info");
    return;
  }

  // 在隐藏的同目录备份中暂存删除；配置更新失败时可以恢复原模板。
  const removal = await stageUserTemplateRemoval(name);
  let updated: string[] = [];
  try {
    if (name !== DEFAULT_TEMPLATE_NAME) {
      const projectDir = await tryResolveGitRepositoryRoot(new GitClient(pi), ctx.cwd);
      updated = await resetTemplateReferences(name, projectDir);
    }
    await removal.commit();
  } catch (error) {
    try {
      await removal.rollback();
    } catch (rollbackError) {
      const detail = rollbackError instanceof Error ? rollbackError.message : String(rollbackError);
      throw new Error(
        `Template removal failed and the staged file could not be restored to ${removal.path}: ${detail}`,
        { cause: error },
      );
    }
    throw error;
  }

  if (name === DEFAULT_TEMPLATE_NAME) {
    ctx.ui.notify(
      `Template "${name}" removed. The built-in default template is now used.\n${removal.path}`,
      "info",
    );
    return;
  }
  if (updated.length > 0) {
    ctx.ui.notify(
      `Template "${name}" removed. Configurations referencing it were reset to "${DEFAULT_TEMPLATE_NAME}":\n${updated.join("\n")}`,
      "info",
    );
    return;
  }
  ctx.ui.notify(`Template "${name}" removed.\n${removal.path}`, "info");
}