import type { UserComposerAttachment } from "@/attachments/types";
import type { PickerItem } from "./new-workspace-picker-item";

// The picker "owns" at most one PR attachment at a time. When the user selects
// a different item the previously-owned PR is removed before the new one is added.
// User-added attachments for other PRs/issues are left untouched.
export function syncPickerPrAttachment(input: {
  attachments: UserComposerAttachment[];
  previousPickerPrNumber: number | null;
  item: PickerItem;
}): { attachments: UserComposerAttachment[]; attachedPrNumber: number | null } {
  let nextAttachments = input.attachments;
  let attachedPrNumber: number | null = null;

  if (input.previousPickerPrNumber !== null) {
    nextAttachments = nextAttachments.filter(
      (attachment) =>
        attachment.kind !== "github_pr" || attachment.item.number !== input.previousPickerPrNumber,
    );
  }

  if (input.item.kind === "github-pr") {
    const selectedPr = input.item.item;
    const hasExistingPrAttachment = nextAttachments.some(
      (attachment) =>
        attachment.kind === "github_pr" && attachment.item.number === selectedPr.number,
    );
    if (!hasExistingPrAttachment) {
      nextAttachments = [...nextAttachments, { kind: "github_pr", item: selectedPr }];
      attachedPrNumber = selectedPr.number;
    }
  }

  return { attachments: nextAttachments, attachedPrNumber };
}

// Suggest a ref picker target derived from composer attachments alone. When the
// user attaches exactly one PR they almost always want the worktree based on
// that PR — surface it as the picker's default so the worktree isn't silently
// branched off main. The caller is responsible for letting manual picks win.
export function deriveAutoPickerItemFromAttachments(
  attachments: ReadonlyArray<UserComposerAttachment>,
): PickerItem | null {
  let onlyPr: Extract<UserComposerAttachment, { kind: "github_pr" }> | null = null;
  for (const attachment of attachments) {
    if (attachment.kind !== "github_pr") continue;
    if (onlyPr) return null;
    onlyPr = attachment;
  }
  return onlyPr ? { kind: "github-pr", item: onlyPr.item } : null;
}