import { randomUUID } from 'node:crypto';
import { isNonEmptyArray, isString } from '@sindresorhus/is';
import { logger } from '../../../logger/index.ts';
import { coerceArray } from '../../../util/array.ts';
import * as git from '../../../util/git/index.ts';
import type { CommitFilesConfig, FileChange } from '../../../util/git/types.ts';
import { hash } from '../../../util/hash.ts';
import type { LongCommitSha } from '../../../util/schema-utils/git.ts';
import { DefaultGitScm } from '../default-scm.ts';
import { client } from './client.ts';
import type { GerritLabels } from './schema.ts';
import { mapBranchStatusToLabel } from './utils.ts';

const CODE_REVIEW_LABEL = 'Code-Review';

/**
 * Gerrit SCM strategy:
 * Instead of implementing custom branch operations, we fetch all open Gerrit changes
 * as virtual branches (refs/remotes/origin/<branchName>) after repository initialization.
 * This allows us to leverage DefaultGitScm for most operations, treating virtual branches
 * as regular Git branches, while minimizing Gerrit API requests.
 */

let repository: string;
let projectLabels: GerritLabels = {};
export function configureScm(repo: string, labels: GerritLabels = {}): void {
  repository = repo;
  projectLabels = labels;
}

/**
 * Returns the max vote value for the "Code-Review" label (some Gerrit
 * projects only allow up to +1), or `null` if the label isn't defined on
 * the project, so the caller can skip voting instead of failing the push.
 */
function getAutoApproveLabelValue(): number | null {
  const codeReviewLabel = projectLabels[CODE_REVIEW_LABEL];
  if (!codeReviewLabel) {
    logger.warn(
      { repository, label: CODE_REVIEW_LABEL },
      'Cannot auto-approve: label is not defined on the project',
    );
    return null;
  }
  return mapBranchStatusToLabel('green', codeReviewLabel);
}

export async function pushForReview(options: {
  sourceRef: string;
  targetBranch: string;
  files: FileChange[];
  autoApprove?: boolean;
  labels?: string[];
}): Promise<boolean> {
  const pushOptions = ['notify=NONE', 'ready'];
  if (options.autoApprove) {
    const value = getAutoApproveLabelValue();
    if (value !== null) {
      pushOptions.push(`label=${CODE_REVIEW_LABEL}+${value}`);
    }
  }
  if (isNonEmptyArray(options.labels)) {
    for (const label of options.labels) {
      pushOptions.push(`hashtag=${label}`);
    }
  }

  return git.pushCommit({
    sourceRef: options.sourceRef,
    targetRef: `refs/for/${options.targetBranch}`,
    files: options.files,
    pushOptions,
  });
}

export class GerritScm extends DefaultGitScm {
  override async commitAndPush(
    commit: CommitFilesConfig,
  ): Promise<LongCommitSha | null> {
    logger.debug(`commitAndPush(${commit.branchName})`);

    const existingChange = await client.getBranchChange(repository, {
      branchName: commit.branchName,
      state: 'open',
      targetBranch: commit.baseBranch,
      requestDetails: ['CURRENT_REVISION'],
    });

    const message = isString(commit.message)
      ? [commit.message]
      : commit.message;

    // In Gerrit, the change subject/title is the first line of the commit message
    // v8 ignore else -- TODO: add test #40625
    if (commit.prTitle) {
      const firstMessageLines = message[0].split('\n');
      firstMessageLines[0] = commit.prTitle;
      message[0] = firstMessageLines.join('\n');
    }

    const changeId = existingChange?.change_id ?? generateChangeId();
    commit.message = message;
    commit.trailers = [
      ...coerceArray(commit.trailers).filter(
        (trailer) =>
          !trailer.startsWith('Renovate-Branch:') &&
          !trailer.startsWith('Change-Id:'),
      ),
      `Renovate-Branch: ${commit.branchName}`,
      `Change-Id: ${changeId}`,
    ];
    // prepareCommit already checks hasDiff('HEAD', 'origin/<branchName>') when
    // force is not set, which works because virtual branches are fetched as
    // refs/remotes/origin/<branchName> during init.  This avoids pushing empty
    // patch sets without a separate diff check.
    const commitResult = await git.prepareCommit(commit);
    if (commitResult) {
      const { commitSha } = commitResult;
      if (existingChange) {
        // Since the change already exists, we push to the same target branch to
        // avoid creating a new change if the base branch has changed.
        // updatePr() will later take care of moving the existing change to a
        // different base branch if needed.
        const pushResult = await pushForReview({
          sourceRef: commit.branchName,
          targetBranch: existingChange.branch,
          files: commit.files,
          autoApprove: commit.autoApprove,
        });
        /* v8 ignore else -- should never happen */
        if (pushResult) {
          const currentRef =
            existingChange.revisions![existingChange.current_revision!].ref;
          await git.setVirtualBranch(
            commit.branchName,
            nextPatchSetRef(currentRef),
            commitSha,
          );
          return commitSha;
        }
      } else {
        logger.debug(`Commit prepared, push deferred to createPr()`);
        return commitSha;
      }
    }
    return null; // empty commit, no changes in this Gerrit Change
  }
}

/**
 * Derive the next patch-set ref from a Gerrit change ref.
 * Gerrit refs follow the pattern `refs/changes/<NN>/<change>/<patchset>`.
 * After a push, Gerrit creates the next patch-set, so we increment the
 * trailing number to keep the virtual branch in sync.
 */
export function nextPatchSetRef(currentRef: string): string {
  const lastSlash = currentRef.lastIndexOf('/');
  const patchSet = parseInt(currentRef.slice(lastSlash + 1), 10);
  return `${currentRef.slice(0, lastSlash + 1)}${patchSet + 1}`;
}

/**
 * This function should generate a Gerrit Change-ID analogous to the commit hook. We avoid the commit hook cause of security concerns.
 * random=$( (whoami ; hostname ; date; cat $1 ; echo $RANDOM) | git hash-object --stdin) prefixed with an 'I'.
 * TODO: Gerrit don't accept longer Change-IDs (sha256), but what happens with this https://git-scm.com/docs/hash-function-transition/ ?
 */
function generateChangeId(): string {
  return `I${hash(randomUUID(), 'sha1')}`;
}