/**
 * Best-effort mirror into the "Interview Prep" user Project — ported from
 * scripts/srs-project.ts. D1 is the truth; a GraphQL failure here becomes a
 * console warning and never blocks a state write. Only problem issues are
 * ever passed in, so topic rows' Target Date is never written.
 *
 * Target Date is the ONLY mirrored column. SRS stage and first-attempt result
 * live exclusively in D1 — they are read from there (charts, digest, /api/stats)
 * and duplicating them into Project single-selects bought nothing but drift and
 * two extra writes per log. Do not re-add them here.
 *
 * Field IDs are resolved by NAME per invocation (a Worker isolate is
 * short-lived; the extra query per mirror burst is irrelevant at this
 * volume and survives field re-creation).
 */
import type { GitHub } from "./github.ts";

const PROJECT_TITLE = "Interview Prep";

interface ProjectInfo {
  id: string;
  targetDate: string;
}

export interface Mirror {
  setTargetDate(issue: number, date: string | null): Promise<void>;
  warnings: string[];
}

export function projectMirror(gh: GitHub, owner: string): Mirror {
  const warnings: string[] = [];
  let info: ProjectInfo | undefined;
  const itemIds = new Map<number, string | undefined>();

  async function resolve(): Promise<ProjectInfo> {
    if (info) return info;
    const data = (await gh.graphql(
      `query($owner: String!, $title: String!) {
        user(login: $owner) {
          projectsV2(first: 10, query: $title) {
            nodes {
              id title
              fields(first: 30) {
                nodes {
                  ... on ProjectV2FieldCommon { id name dataType }
                }
              }
            }
          }
        }
      }`,
      { owner, title: PROJECT_TITLE },
    )) as {
      user: {
        projectsV2: {
          nodes: {
            id: string;
            title: string;
            fields: {
              nodes: { id: string; name: string }[];
            };
          }[];
        };
      };
    };
    const node = data.user.projectsV2.nodes.find((n) => n.title === PROJECT_TITLE);
    if (!node) throw new Error(`project "${PROJECT_TITLE}" not found for @${owner}`);
    const date = node.fields.nodes.find((n) => n.name === "Target Date");
    if (!date) throw new Error(`date field "Target Date" missing`);
    info = { id: node.id, targetDate: date.id };
    return info;
  }

  async function itemId(issue: number): Promise<string> {
    if (itemIds.has(issue)) {
      const cached = itemIds.get(issue);
      if (!cached) throw new Error(`issue #${issue} is not in the project`);
      return cached;
    }
    const project = await resolve();
    const [repoOwner, repoName] = gh.repo.split("/");
    const data = (await gh.graphql(
      `query($owner: String!, $name: String!, $issue: Int!) {
        repository(owner: $owner, name: $name) {
          issue(number: $issue) {
            projectItems(first: 10, includeArchived: true) {
              nodes { id project { id } }
            }
          }
        }
      }`,
      { owner: repoOwner, name: repoName, issue },
    )) as {
      repository: { issue: { projectItems: { nodes: { id: string; project: { id: string } }[] } } };
    };
    const item = data.repository.issue.projectItems.nodes.find((n) => n.project.id === project.id);
    itemIds.set(issue, item?.id);
    if (!item) throw new Error(`issue #${issue} is not in the project`);
    return item.id;
  }

  async function setField(issue: number, fieldId: string, value: object): Promise<void> {
    const project = await resolve();
    await gh.graphql(
      `mutation($project: ID!, $item: ID!, $field: ID!, $value: ProjectV2FieldValue!) {
        updateProjectV2ItemFieldValue(
          input: { projectId: $project, itemId: $item, fieldId: $field, value: $value }
        ) { projectV2Item { id } }
      }`,
      { project: project.id, item: await itemId(issue), field: fieldId, value },
    );
  }

  async function attempt(what: string, op: () => Promise<void>): Promise<void> {
    try {
      await op();
    } catch (err) {
      const message = `mirror ${what}: ${err instanceof Error ? err.message : String(err)}`;
      warnings.push(message);
      console.warn(message); // observability picks this up; never rethrow
    }
  }

  return {
    warnings,
    setTargetDate: (issue, date) =>
      attempt(`Target Date #${issue}`, async () => {
        const project = await resolve();
        if (date === null) {
          await gh.graphql(
            `mutation($project: ID!, $item: ID!, $field: ID!) {
              clearProjectV2ItemFieldValue(
                input: { projectId: $project, itemId: $item, fieldId: $field }
              ) { projectV2Item { id } }
            }`,
            { project: project.id, item: await itemId(issue), field: project.targetDate },
          );
        } else {
          await setField(issue, project.targetDate, { date });
        }
      }),
  };
}