import type { Task } from "@fusion/core";
import type { BoardWorkflowColumn, BoardWorkflowsPayload } from "../api";

export interface WorkflowStatusCounts {
  todo: number;
  inProgress: number;
  done: number;
  merging: number;
}

const EMPTY_COUNTS = (): WorkflowStatusCounts => ({
  todo: 0,
  inProgress: 0,
  done: 0,
  merging: 0,
});

type WorkflowStatusBucket = keyof WorkflowStatusCounts | "excluded";

const MERGING_STATUSES = new Set(["merging", "merging-pr", "merging-fix"]);

/**
 * FNXC:WorkflowSwitcher 2026-06-20-00:09:
 * The board/list workflow dropdown must show compact Todo, In Progress, and Done task counts for every selectable workflow without duplicating logic across render surfaces.
 * Use workflow column flags as the source of truth: archived columns are excluded, complete columns count as Done, active non-intake WIP columns count as In Progress, and all remaining visible work counts as Todo/not-yet-started.
 *
 * FNXC:WorkflowSwitcher 2026-06-21-00:00:
 * Built-in linear workflows synthesize canonical lifecycle columns with empty traits, so their resolved flags cannot identify Done, In Progress, or Archived buckets.
 * Fall back to canonical lifecycle column ids only after flag-based classification fails, keeping trait-bearing workflows authoritative while preventing Done tasks in Quick fix-style lanes from being miscounted.
 */
function classifyWorkflowStatusColumn(
  column: BoardWorkflowColumn
): WorkflowStatusBucket {
  if (column.flags.archived) return "excluded";
  if (column.flags.complete) return "done";
  if (column.flags.countsTowardWip && !column.flags.intake) return "inProgress";

  switch (column.id) {
    case "archived":
      return "excluded";
    case "done":
      return "done";
    case "in-progress":
      return "inProgress";
    default:
      return "todo";
  }
}

export function computeWorkflowStatusCounts(
  tasks: readonly Task[] | null | undefined,
  boardWorkflows: BoardWorkflowsPayload | null | undefined
): Map<string, WorkflowStatusCounts> {
  const countsByWorkflow = new Map<string, WorkflowStatusCounts>();
  if (!boardWorkflows) return countsByWorkflow;

  const workflowsById = new Map(
    boardWorkflows.workflows.map((workflow) => [workflow.id, workflow])
  );
  const columnsByWorkflowId = new Map<
    string,
    Map<string, BoardWorkflowColumn>
  >();

  for (const workflow of boardWorkflows.workflows) {
    countsByWorkflow.set(workflow.id, EMPTY_COUNTS());
    columnsByWorkflowId.set(
      workflow.id,
      new Map(workflow.columns.map((column) => [column.id, column]))
    );
  }

  if (!tasks?.length) return countsByWorkflow;

  for (const task of tasks) {
    const workflowId =
      boardWorkflows.taskWorkflowIds[task.id] ??
      boardWorkflows.defaultWorkflowId;
    const workflow = workflowsById.get(workflowId);
    if (!workflow) continue;

    const column = columnsByWorkflowId.get(workflow.id)?.get(task.column);
    if (!column) continue;

    const bucket = classifyWorkflowStatusColumn(column);
    if (bucket === "excluded") continue;

    const counts = countsByWorkflow.get(workflow.id) ?? EMPTY_COUNTS();
    counts[bucket] += 1;
    if (MERGING_STATUSES.has(task.status ?? "")) {
      /*
      FNXC:WorkflowSwitcher 2026-06-22-20:30:
      Workflow boards need a visible flashing indicator in the workflow dropdown when any task assigned to that workflow is actively merging, independent of whether the workflow's review/merge column buckets as Todo or In Progress.
      */
      counts.merging += 1;
    }
    countsByWorkflow.set(workflow.id, counts);
  }

  return countsByWorkflow;
}