/**
 * 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.
 *
 * Field/option IDs are resolved by NAME per invocation (a Worker isolate is
 * short-lived; the two extra queries per mirror burst are irrelevant at this
 * volume and survive field re-creation).
 */
import type { GitHub } from "./github.ts";

const PROJECT_TITLE = "Interview Prep";

interface SelectField {
  id: string;
  options: Record<string, string>;
}

interface ProjectInfo {
  id: string;
  targetDate: string;
  srsStage: SelectField;
  firstAttempt: SelectField;
}

export interface Mirror {
  setTargetDate(issue: number, date: string | null): Promise<void>;
  setStage(issue: number, stage: string): Promise<void>;
  setFirstAttempt(issue: number, result: string): 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: $title) {
            nodes {
              id title
              fields(first: 30) {
                nodes {
                  ... on ProjectV2FieldCommon { id name dataType }
                  ... on ProjectV2SingleSelectField { id name options { id name } }
                }
              }
            }
          }
        }
      }`,
      { owner, title: PROJECT_TITLE },
    )) as {
      user: {
        projectsV2: {
          nodes: {
            id: string;
            title: string;
            fields: {
              nodes: { id: string; name: string; options?: { id: string; name: string }[] }[];
            };
          }[];
        };
      };
    };
    const node = data.user.projectsV2.nodes.find((n) => n.title === PROJECT_TITLE);
    if (!node) throw new Error(`project "${PROJECT_TITLE}" not found for @${owner}`);
    const select = (name: string): SelectField => {
      const f = node.fields.nodes.find((n) => n.name === name);
      if (!f?.options) throw new Error(`single-select field "${name}" missing`);
      return { id: f.id, options: Object.fromEntries(f.options.map((o) => [o.name, o.id])) };
    };
    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,
      srsStage: select("SRS Stage"),
      firstAttempt: select("First Attempt"),
    };
    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: $field }
              ) { projectV2Item { id } }
            }`,
            { project: project.id, item: await itemId(issue), field: project.targetDate },
          );
        } else {
          await setField(issue, project.targetDate, { date });
        }
      }),
    setStage: (issue, stage) =>
      attempt(`SRS Stage #${issue}`, async () => {
        const project = await resolve();
        const option = project.srsStage.options[stage];
        if (!option) throw new Error(`no option "${stage}"`);
        await setField(issue, project.srsStage.id, { singleSelectOptionId: option });
      }),
    setFirstAttempt: (issue, result) =>
      attempt(`First Attempt #${issue}`, async () => {
        const project = await resolve();
        const option = project.firstAttempt.options[result];
        if (!option) throw new Error(`no option "${result}"`);
        await setField(issue, project.firstAttempt.id, { singleSelectOptionId: option });
      }),
  };
}