import { and, asc, eq, inArray, isNull } from "drizzle-orm";
import type { Db } from "@paperclipai/db";
import { documents, issueComments, issueDocuments, issueReferenceMentions, issues } from "@paperclipai/db";
import type {
  IssueReferenceSource,
  IssueReferenceSourceKind,
  IssueRelatedWorkItem,
  IssueRelatedWorkSummary,
  IssueRelationIssueSummary,
} from "@paperclipai/shared";
import { extractIssueReferenceMatches } from "@paperclipai/shared";
import { notFound } from "../errors.js";

const SOURCE_KIND_ORDER: Record<IssueReferenceSourceKind, number> = {
  title: 0,
  description: 1,
  document: 2,
  comment: 3,
};

function sourceLabel(kind: IssueReferenceSourceKind, documentKey: string | null): string {
  if (kind === "document") return documentKey?.trim() || "document";
  return kind;
}

function sourceWhere(
  input: {
    companyId?: string;
    sourceIssueId?: string;
    sourceKind: IssueReferenceSourceKind;
    sourceRecordId?: string | null;
  },
) {
  const conditions = [eq(issueReferenceMentions.sourceKind, input.sourceKind)];
  if (input.companyId) conditions.push(eq(issueReferenceMentions.companyId, input.companyId));
  if (input.sourceIssueId) conditions.push(eq(issueReferenceMentions.sourceIssueId, input.sourceIssueId));
  if (input.sourceRecordId) {
    conditions.push(eq(issueReferenceMentions.sourceRecordId, input.sourceRecordId));
  } else {
    conditions.push(isNull(issueReferenceMentions.sourceRecordId));
  }
  return and(...conditions);
}

function toIssueSummary(row: {
  relatedIssueId: string;
  relatedIssueIdentifier: string | null;
  relatedIssueTitle: string;
  relatedIssueStatus: IssueRelationIssueSummary["status"];
  relatedIssuePriority: IssueRelationIssueSummary["priority"];
  relatedIssueAssigneeAgentId: string | null;
  relatedIssueAssigneeUserId: string | null;
}): IssueRelationIssueSummary {
  return {
    id: row.relatedIssueId,
    identifier: row.relatedIssueIdentifier,
    title: row.relatedIssueTitle,
    status: row.relatedIssueStatus,
    priority: row.relatedIssuePriority,
    assigneeAgentId: row.relatedIssueAssigneeAgentId,
    assigneeUserId: row.relatedIssueAssigneeUserId,
  };
}

function sortSources(a: IssueReferenceSource, b: IssueReferenceSource) {
  const orderDelta = SOURCE_KIND_ORDER[a.kind] - SOURCE_KIND_ORDER[b.kind];
  if (orderDelta !== 0) return orderDelta;
  const labelDelta = a.label.localeCompare(b.label);
  if (labelDelta !== 0) return labelDelta;
  return (a.sourceRecordId ?? "").localeCompare(b.sourceRecordId ?? "");
}

function sortRelatedWork(a: IssueRelatedWorkItem, b: IssueRelatedWorkItem) {
  if (b.mentionCount !== a.mentionCount) return b.mentionCount - a.mentionCount;
  const leftLabel = a.issue.identifier ?? a.issue.title;
  const rightLabel = b.issue.identifier ?? b.issue.title;
  return leftLabel.localeCompare(rightLabel);
}

function emptySummary(): IssueRelatedWorkSummary {
  return {
    outbound: [],
    inbound: [],
  };
}

function diffIssueSummaries(
  before: IssueRelatedWorkSummary,
  after: IssueRelatedWorkSummary,
): {
  addedReferencedIssues: IssueRelationIssueSummary[];
  removedReferencedIssues: IssueRelationIssueSummary[];
  currentReferencedIssues: IssueRelationIssueSummary[];
} {
  const beforeById = new Map(before.outbound.map((item) => [item.issue.id, item.issue]));
  const afterById = new Map(after.outbound.map((item) => [item.issue.id, item.issue]));

  return {
    addedReferencedIssues: after.outbound
      .map((item) => item.issue)
      .filter((issue) => !beforeById.has(issue.id)),
    removedReferencedIssues: before.outbound
      .map((item) => item.issue)
      .filter((issue) => !afterById.has(issue.id)),
    currentReferencedIssues: after.outbound.map((item) => item.issue),
  };
}

export function issueReferenceService(db: Db) {
  async function replaceSourceMentions(
    input: {
      companyId: string;
      sourceIssueId: string;
      sourceKind: IssueReferenceSourceKind;
      sourceRecordId: string | null;
      documentKey: string | null;
      text: string | null | undefined;
    },
    dbOrTx: any = db,
  ) {
    const matches = extractIssueReferenceMatches(input.text ?? "");
    const identifiers = matches.map((match) => match.identifier);
    type ResolvedTargetRow = {
      id: string;
      identifier: string | null;
    };

    const resolvedTargets: ResolvedTargetRow[] = identifiers.length > 0
      ? await dbOrTx
        .select({
          id: issues.id,
          identifier: issues.identifier,
        })
        .from(issues)
        .where(and(eq(issues.companyId, input.companyId), inArray(issues.identifier, identifiers)))
      : [];
    const targetByIdentifier = new Map<string, string>(
      resolvedTargets
        .filter((row): row is ResolvedTargetRow & { identifier: string } => typeof row.identifier === "string")
        .map((row) => [row.identifier, row.id]),
    );

    await dbOrTx.delete(issueReferenceMentions).where(sourceWhere(input));

    if (matches.length === 0) return;

    const seenTargetIds = new Set<string>();
    const values = matches.flatMap((match) => {
      const targetIssueId = targetByIdentifier.get(match.identifier);
      if (!targetIssueId || targetIssueId === input.sourceIssueId || seenTargetIds.has(targetIssueId)) {
        return [];
      }
      seenTargetIds.add(targetIssueId);
      return [{
        companyId: input.companyId,
        sourceIssueId: input.sourceIssueId,
        targetIssueId,
        sourceKind: input.sourceKind,
        sourceRecordId: input.sourceRecordId,
        documentKey: input.documentKey,
        matchedText: match.matchedText,
      }];
    });

    if (values.length > 0) {
      await dbOrTx.insert(issueReferenceMentions).values(values);
    }
  }

  async function issueById(issueId: string, dbOrTx: any = db) {
    return dbOrTx
      .select({
        id: issues.id,
        companyId: issues.companyId,
        title: issues.title,
        description: issues.description,
      })
      .from(issues)
      .where(eq(issues.id, issueId))
      .then((rows: Array<{ id: string; companyId: string; title: string; description: string | null }>) => rows[0] ?? null);
  }

  async function syncIssue(issueId: string, dbOrTx: any = db) {
    const runSync = async (tx: any) => {
      const issue = await issueById(issueId, tx);
      if (!issue) throw notFound("Issue not found");

      await replaceSourceMentions({
        companyId: issue.companyId,
        sourceIssueId: issue.id,
        sourceKind: "title",
        sourceRecordId: null,
        documentKey: null,
        text: issue.title,
      }, tx);

      await replaceSourceMentions({
        companyId: issue.companyId,
        sourceIssueId: issue.id,
        sourceKind: "description",
        sourceRecordId: null,
        documentKey: null,
        text: issue.description,
      }, tx);
    };

    return dbOrTx === db ? db.transaction(runSync) : runSync(dbOrTx);
  }

  async function syncComment(commentId: string, dbOrTx: any = db) {
    const comment = await dbOrTx
      .select({
        id: issueComments.id,
        companyId: issueComments.companyId,
        issueId: issueComments.issueId,
        body: issueComments.body,
      })
      .from(issueComments)
      .where(eq(issueComments.id, commentId))
      .then((rows: Array<{ id: string; companyId: string; issueId: string; body: string }>) => rows[0] ?? null);
    if (!comment) throw notFound("Issue comment not found");

    await replaceSourceMentions({
      companyId: comment.companyId,
      sourceIssueId: comment.issueId,
      sourceKind: "comment",
      sourceRecordId: comment.id,
      documentKey: null,
      text: comment.body,
    }, dbOrTx);
  }

  async function syncDocument(documentId: string, dbOrTx: any = db) {
    const document = await dbOrTx
      .select({
        documentId: documents.id,
        companyId: documents.companyId,
        issueId: issueDocuments.issueId,
        key: issueDocuments.key,
        body: documents.latestBody,
      })
      .from(issueDocuments)
      .innerJoin(documents, eq(issueDocuments.documentId, documents.id))
      .where(eq(documents.id, documentId))
      .then((rows: Array<{ documentId: string; companyId: string; issueId: string; key: string; body: string }>) => rows[0] ?? null);

    if (!document) {
      await dbOrTx
        .delete(issueReferenceMentions)
        .where(and(eq(issueReferenceMentions.sourceKind, "document"), eq(issueReferenceMentions.sourceRecordId, documentId)));
      return;
    }

    await replaceSourceMentions({
      companyId: document.companyId,
      sourceIssueId: document.issueId,
      sourceKind: "document",
      sourceRecordId: document.documentId,
      documentKey: document.key,
      text: document.body,
    }, dbOrTx);
  }

  async function deleteDocumentSource(documentId: string, dbOrTx: any = db) {
    await dbOrTx
      .delete(issueReferenceMentions)
      .where(and(eq(issueReferenceMentions.sourceKind, "document"), eq(issueReferenceMentions.sourceRecordId, documentId)));
  }

  async function syncAllForIssue(issueId: string, dbOrTx: any = db) {
    const issue = await issueById(issueId, dbOrTx);
    if (!issue) throw notFound("Issue not found");

    await syncIssue(issueId, dbOrTx);

    const [comments, docs] = await Promise.all([
      dbOrTx
        .select({ id: issueComments.id })
        .from(issueComments)
        .where(eq(issueComments.issueId, issueId)),
      dbOrTx
        .select({ id: documents.id })
        .from(issueDocuments)
        .innerJoin(documents, eq(issueDocuments.documentId, documents.id))
        .where(eq(issueDocuments.issueId, issueId)),
    ]);

    for (const comment of comments) {
      await syncComment(comment.id, dbOrTx);
    }
    for (const doc of docs) {
      await syncDocument(doc.id, dbOrTx);
    }
  }

  async function syncAllForCompany(companyId: string, dbOrTx: any = db) {
    const issueRows = await dbOrTx
      .select({ id: issues.id })
      .from(issues)
      .where(eq(issues.companyId, companyId))
      .orderBy(asc(issues.createdAt), asc(issues.id));

    for (const issue of issueRows) {
      await syncAllForIssue(issue.id, dbOrTx);
    }
  }

  async function listIssueReferenceSummary(issueId: string, dbOrTx: any = db): Promise<IssueRelatedWorkSummary> {
      const issue = await issueById(issueId, dbOrTx);
      if (!issue) throw notFound("Issue not found");

      const [outboundRows, inboundRows] = await Promise.all([
        dbOrTx
          .select({
            relatedIssueId: issues.id,
            relatedIssueIdentifier: issues.identifier,
            relatedIssueTitle: issues.title,
            relatedIssueStatus: issues.status,
            relatedIssuePriority: issues.priority,
            relatedIssueAssigneeAgentId: issues.assigneeAgentId,
            relatedIssueAssigneeUserId: issues.assigneeUserId,
            sourceKind: issueReferenceMentions.sourceKind,
            sourceRecordId: issueReferenceMentions.sourceRecordId,
            documentKey: issueReferenceMentions.documentKey,
            matchedText: issueReferenceMentions.matchedText,
          })
          .from(issueReferenceMentions)
          .innerJoin(issues, eq(issueReferenceMentions.targetIssueId, issues.id))
          .where(and(
            eq(issueReferenceMentions.companyId, issue.companyId),
            eq(issueReferenceMentions.sourceIssueId, issueId),
          )),
        dbOrTx
          .select({
            relatedIssueId: issues.id,
            relatedIssueIdentifier: issues.identifier,
            relatedIssueTitle: issues.title,
            relatedIssueStatus: issues.status,
            relatedIssuePriority: issues.priority,
            relatedIssueAssigneeAgentId: issues.assigneeAgentId,
            relatedIssueAssigneeUserId: issues.assigneeUserId,
            sourceKind: issueReferenceMentions.sourceKind,
            sourceRecordId: issueReferenceMentions.sourceRecordId,
            documentKey: issueReferenceMentions.documentKey,
            matchedText: issueReferenceMentions.matchedText,
          })
          .from(issueReferenceMentions)
          .innerJoin(issues, eq(issueReferenceMentions.sourceIssueId, issues.id))
          .where(and(
            eq(issueReferenceMentions.companyId, issue.companyId),
            eq(issueReferenceMentions.targetIssueId, issueId),
          )),
      ]);

      const mapRows = (rows: Array<{
        relatedIssueId: string;
        relatedIssueIdentifier: string | null;
        relatedIssueTitle: string;
        relatedIssueStatus: IssueRelationIssueSummary["status"];
        relatedIssuePriority: IssueRelationIssueSummary["priority"];
        relatedIssueAssigneeAgentId: string | null;
        relatedIssueAssigneeUserId: string | null;
        sourceKind: IssueReferenceSourceKind;
        sourceRecordId: string | null;
        documentKey: string | null;
        matchedText: string | null;
      }>) => {
        const grouped = new Map<string, IssueRelatedWorkItem>();
        for (const row of rows) {
          const existing = grouped.get(row.relatedIssueId) ?? {
            issue: toIssueSummary(row),
            mentionCount: 0,
            sources: [],
          };
          existing.mentionCount += 1;
          existing.sources.push({
            kind: row.sourceKind,
            sourceRecordId: row.sourceRecordId,
            label: sourceLabel(row.sourceKind, row.documentKey),
            matchedText: row.matchedText,
          });
          grouped.set(row.relatedIssueId, existing);
        }

        return [...grouped.values()]
          .map((item) => ({ ...item, sources: [...item.sources].sort(sortSources) }))
          .sort(sortRelatedWork);
      };

      return {
        outbound: mapRows(outboundRows),
        inbound: mapRows(inboundRows),
      };
  }

  return {
    syncIssue,
    syncComment,
    syncDocument,
    deleteDocumentSource,
    syncAllForIssue,
    syncAllForCompany,
    listIssueReferenceSummary,
    diffIssueReferenceSummary: diffIssueSummaries,
    emptySummary,
  };
}