// Copyright (C) 2010 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package com.google.gerrit.server.project;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.gerrit.common.data.Permission;
import com.google.gerrit.common.data.PermissionRange;
import com.google.gerrit.common.data.PermissionRule;
import com.google.gerrit.extensions.restapi.AuthException;
import com.google.gerrit.reviewdb.client.BooleanProjectConfig;
import com.google.gerrit.reviewdb.client.Change;
import com.google.gerrit.reviewdb.client.Project;
import com.google.gerrit.reviewdb.client.RefNames;
import com.google.gerrit.server.CurrentUser;
import com.google.gerrit.server.notedb.ChangeNotes;
import com.google.gerrit.server.permissions.FailedPermissionBackend;
import com.google.gerrit.server.permissions.PermissionBackend.ForChange;
import com.google.gerrit.server.permissions.PermissionBackend.ForRef;
import com.google.gerrit.server.permissions.PermissionBackendException;
import com.google.gerrit.server.permissions.RefPermission;
import com.google.gerrit.server.query.change.ChangeData;
import com.google.gerrit.server.util.MagicBranch;
import com.google.gwtorm.server.OrmException;
import com.google.inject.util.Providers;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

/** Manages access control for Git references (aka branches, tags). */
class RefControl {
  private final ProjectControl projectControl;
  private final String refName;

  /** All permissions that apply to this reference. */
  private final PermissionCollection relevant;

  /** Cached set of permissions matching this user. */
  private final Map<String, List<PermissionRule>> effective;

  private Boolean owner;
  private Boolean canForgeAuthor;
  private Boolean canForgeCommitter;
  private Boolean isVisible;

  RefControl(ProjectControl projectControl, String ref, PermissionCollection relevant) {
    this.projectControl = projectControl;
    this.refName = ref;
    this.relevant = relevant;
    this.effective = new HashMap<>();
  }

  ProjectControl getProjectControl() {
    return projectControl;
  }

  CurrentUser getUser() {
    return projectControl.getUser();
  }

  RefControl forUser(CurrentUser who) {
    ProjectControl newCtl = projectControl.forUser(who);
    if (relevant.isUserSpecific()) {
      return newCtl.controlForRef(refName);
    }
    return new RefControl(newCtl, refName, relevant);
  }

  /** Is this user a ref owner? */
  boolean isOwner() {
    if (owner == null) {
      if (canPerform(Permission.OWNER)) {
        owner = true;

      } else {
        owner = projectControl.isOwner();
      }
    }
    return owner;
  }

  /** Can this user see this reference exists? */
  boolean isVisible() {
    if (isVisible == null) {
      isVisible = getUser().isInternalUser() || canPerform(Permission.READ);
    }
    return isVisible;
  }

  /** @return true if this user can add a new patch set to this ref */
  boolean canAddPatchSet() {
    return projectControl
        .controlForRef(MagicBranch.NEW_CHANGE + refName)
        .canPerform(Permission.ADD_PATCH_SET);
  }

  /** @return true if this user can rebase changes on this ref */
  boolean canRebase() {
    return canPerform(Permission.REBASE);
  }

  /** @return true if this user can submit patch sets to this ref */
  boolean canSubmit(boolean isChangeOwner) {
    if (RefNames.REFS_CONFIG.equals(refName)) {
      // Always allow project owners to submit configuration changes.
      // Submitting configuration changes modifies the access control
      // rules. Allowing this to be done by a non-project-owner opens
      // a security hole enabling editing of access rules, and thus
      // granting of powers beyond submitting to the configuration.
      return projectControl.isOwner();
    }
    return canPerform(Permission.SUBMIT, isChangeOwner);
  }

  /** @return true if this user can force edit topic names. */
  boolean canForceEditTopicName() {
    return canForcePerform(Permission.EDIT_TOPIC_NAME);
  }

  /** The range of permitted values associated with a label permission. */
  PermissionRange getRange(String permission) {
    return getRange(permission, false);
  }

  /** The range of permitted values associated with a label permission. */
  PermissionRange getRange(String permission, boolean isChangeOwner) {
    if (Permission.hasRange(permission)) {
      return toRange(permission, access(permission, isChangeOwner));
    }
    return null;
  }

  /** True if the user is blocked from using this permission. */
  boolean isBlocked(String permissionName) {
    return !doCanPerform(permissionName, false, true);
  }

  /** True if the user has this permission. Works only for non labels. */
  boolean canPerform(String permissionName) {
    return canPerform(permissionName, false);
  }

  ForRef asForRef() {
    return new ForRefImpl();
  }

  private boolean canPerform(String permissionName, boolean isChangeOwner) {
    return doCanPerform(permissionName, isChangeOwner, false);
  }

  private boolean canUpload() {
    return projectControl.controlForRef("refs/for/" + refName).canPerform(Permission.PUSH);
  }

  /** @return true if this user can submit merge patch sets to this ref */
  private boolean canUploadMerges() {
    return projectControl.controlForRef("refs/for/" + refName).canPerform(Permission.PUSH_MERGE);
  }

  /** @return true if the user can update the reference as a fast-forward. */
  private boolean canUpdate() {
    if (RefNames.REFS_CONFIG.equals(refName) && !projectControl.isOwner()) {
      // Pushing requires being at least project owner, in addition to push.
      // Pushing configuration changes modifies the access control
      // rules. Allowing this to be done by a non-project-owner opens
      // a security hole enabling editing of access rules, and thus
      // granting of powers beyond pushing to the configuration.

      // On the AllProjects project the owner access right cannot be assigned,
      // this why for the AllProjects project we allow administrators to push
      // configuration changes if they have push without being project owner.
      if (!(projectControl.getProjectState().isAllProjects() && projectControl.isAdmin())) {
        return false;
      }
    }
    return canPerform(Permission.PUSH);
  }

  /** @return true if the user can rewind (force push) the reference. */
  private boolean canForceUpdate() {
    if (canPushWithForce()) {
      return true;
    }

    switch (getUser().getAccessPath()) {
      case GIT:
        return false;

      case JSON_RPC:
      case REST_API:
      case SSH_COMMAND:
      case UNKNOWN:
      case WEB_BROWSER:
      default:
        return (isOwner() && !isForceBlocked(Permission.PUSH)) || projectControl.isAdmin();
    }
  }

  private boolean canPushWithForce() {
    if (RefNames.REFS_CONFIG.equals(refName) && !projectControl.isOwner()) {
      // Pushing requires being at least project owner, in addition to push.
      // Pushing configuration changes modifies the access control
      // rules. Allowing this to be done by a non-project-owner opens
      // a security hole enabling editing of access rules, and thus
      // granting of powers beyond pushing to the configuration.
      return false;
    }
    return canForcePerform(Permission.PUSH);
  }

  /**
   * Determines whether the user can delete the Git ref controlled by this object.
   *
   * @return {@code true} if the user specified can delete a Git ref.
   */
  private boolean canDelete() {
    if (RefNames.REFS_CONFIG.equals(refName)) {
      // Never allow removal of the refs/meta/config branch.
      // Deleting the branch would destroy all Gerrit specific
      // metadata about the project, including its access rules.
      // If a project is to be removed from Gerrit, its repository
      // should be removed first.
      return false;
    }

    switch (getUser().getAccessPath()) {
      case GIT:
        return canPushWithForce() || canPerform(Permission.DELETE);

      case JSON_RPC:
      case REST_API:
      case SSH_COMMAND:
      case UNKNOWN:
      case WEB_BROWSER:
      default:
        return (isOwner() && !isForceBlocked(Permission.PUSH))
            || canPushWithForce()
            || canPerform(Permission.DELETE)
            || projectControl.isAdmin();
    }
  }

  /** @return true if this user can forge the author line in a commit. */
  private boolean canForgeAuthor() {
    if (canForgeAuthor == null) {
      canForgeAuthor = canPerform(Permission.FORGE_AUTHOR);
    }
    return canForgeAuthor;
  }

  /** @return true if this user can forge the committer line in a commit. */
  private boolean canForgeCommitter() {
    if (canForgeCommitter == null) {
      canForgeCommitter = canPerform(Permission.FORGE_COMMITTER);
    }
    return canForgeCommitter;
  }

  /** @return true if this user can forge the server on the committer line. */
  private boolean canForgeGerritServerIdentity() {
    return canPerform(Permission.FORGE_SERVER);
  }

  private static class AllowedRange {
    private int allowMin;
    private int allowMax;
    private int blockMin = Integer.MIN_VALUE;
    private int blockMax = Integer.MAX_VALUE;

    void update(PermissionRule rule) {
      if (rule.isBlock()) {
        blockMin = Math.max(blockMin, rule.getMin());
        blockMax = Math.min(blockMax, rule.getMax());
      } else {
        allowMin = Math.min(allowMin, rule.getMin());
        allowMax = Math.max(allowMax, rule.getMax());
      }
    }

    int getAllowMin() {
      return allowMin;
    }

    int getAllowMax() {
      return allowMax;
    }

    int getBlockMin() {
      // ALLOW wins over BLOCK on the same project
      return Math.min(blockMin, allowMin - 1);
    }

    int getBlockMax() {
      // ALLOW wins over BLOCK on the same project
      return Math.max(blockMax, allowMax + 1);
    }
  }

  private PermissionRange toRange(String permissionName, List<PermissionRule> ruleList) {
    Map<ProjectRef, AllowedRange> ranges = new HashMap<>();
    for (PermissionRule rule : ruleList) {
      ProjectRef p = relevant.getRuleProps(rule);
      AllowedRange r = ranges.get(p);
      if (r == null) {
        r = new AllowedRange();
        ranges.put(p, r);
      }
      r.update(rule);
    }
    int allowMin = 0;
    int allowMax = 0;
    int blockMin = Integer.MIN_VALUE;
    int blockMax = Integer.MAX_VALUE;
    for (AllowedRange r : ranges.values()) {
      allowMin = Math.min(allowMin, r.getAllowMin());
      allowMax = Math.max(allowMax, r.getAllowMax());
      blockMin = Math.max(blockMin, r.getBlockMin());
      blockMax = Math.min(blockMax, r.getBlockMax());
    }

    // BLOCK wins over ALLOW across projects
    int min = Math.max(allowMin, blockMin + 1);
    int max = Math.min(allowMax, blockMax - 1);
    return new PermissionRange(permissionName, min, max);
  }

  private boolean doCanPerform(String permissionName, boolean isChangeOwner, boolean blockOnly) {
    List<PermissionRule> access = access(permissionName, isChangeOwner);
    List<PermissionRule> overridden = relevant.getOverridden(permissionName);
    Set<ProjectRef> allows = new HashSet<>();
    Set<ProjectRef> blocks = new HashSet<>();
    for (PermissionRule rule : access) {
      if (rule.isBlock() && !rule.getForce()) {
        blocks.add(relevant.getRuleProps(rule));
      } else {
        allows.add(relevant.getRuleProps(rule));
      }
    }
    for (PermissionRule rule : overridden) {
      blocks.remove(relevant.getRuleProps(rule));
    }
    blocks.removeAll(allows);
    return blocks.isEmpty() && (!allows.isEmpty() || blockOnly);
  }

  /** True if the user has force this permission. Works only for non labels. */
  private boolean canForcePerform(String permissionName) {
    List<PermissionRule> access = access(permissionName);
    List<PermissionRule> overridden = relevant.getOverridden(permissionName);
    Set<ProjectRef> allows = new HashSet<>();
    Set<ProjectRef> blocks = new HashSet<>();
    for (PermissionRule rule : access) {
      if (rule.isBlock()) {
        blocks.add(relevant.getRuleProps(rule));
      } else if (rule.getForce()) {
        allows.add(relevant.getRuleProps(rule));
      }
    }
    for (PermissionRule rule : overridden) {
      if (rule.getForce()) {
        blocks.remove(relevant.getRuleProps(rule));
      }
    }
    blocks.removeAll(allows);
    return blocks.isEmpty() && !allows.isEmpty();
  }

  /** True if for this permission force is blocked for the user. Works only for non labels. */
  private boolean isForceBlocked(String permissionName) {
    List<PermissionRule> access = access(permissionName);
    List<PermissionRule> overridden = relevant.getOverridden(permissionName);
    Set<ProjectRef> allows = new HashSet<>();
    Set<ProjectRef> blocks = new HashSet<>();
    for (PermissionRule rule : access) {
      if (rule.isBlock()) {
        blocks.add(relevant.getRuleProps(rule));
      } else if (rule.getForce()) {
        allows.add(relevant.getRuleProps(rule));
      }
    }
    for (PermissionRule rule : overridden) {
      if (rule.getForce()) {
        blocks.remove(relevant.getRuleProps(rule));
      }
    }
    blocks.removeAll(allows);
    return !blocks.isEmpty();
  }

  /** Rules for the given permission, or the empty list. */
  private List<PermissionRule> access(String permissionName) {
    return access(permissionName, false);
  }

  /** Rules for the given permission, or the empty list. */
  private List<PermissionRule> access(String permissionName, boolean isChangeOwner) {
    List<PermissionRule> rules = effective.get(permissionName);
    if (rules != null) {
      return rules;
    }

    rules = relevant.getPermission(permissionName);

    List<PermissionRule> mine = new ArrayList<>(rules.size());
    for (PermissionRule rule : rules) {
      if (projectControl.match(rule, isChangeOwner)) {
        mine.add(rule);
      }
    }

    if (mine.isEmpty()) {
      mine = Collections.emptyList();
    }
    effective.put(permissionName, mine);
    return mine;
  }

  private class ForRefImpl extends ForRef {
    @Override
    public ForRef user(CurrentUser user) {
      return forUser(user).asForRef().database(db);
    }

    @Override
    public ForChange change(ChangeData cd) {
      try {
        // TODO(hiesel) Force callers to call database() and use db instead of cd.db()
        return getProjectControl()
            .controlFor(cd.db(), cd.change())
            .asForChange(cd, Providers.of(cd.db()));
      } catch (OrmException e) {
        return FailedPermissionBackend.change("unavailable", e);
      }
    }

    @Override
    public ForChange change(ChangeNotes notes) {
      Project.NameKey project = getProjectControl().getProject().getNameKey();
      Change change = notes.getChange();
      checkArgument(
          project.equals(change.getProject()),
          "expected change in project %s, not %s",
          project,
          change.getProject());
      return getProjectControl().controlFor(notes).asForChange(null, db);
    }

    @Override
    public ForChange indexedChange(ChangeData cd, ChangeNotes notes) {
      return getProjectControl().controlFor(notes).asForChange(cd, db);
    }

    @Override
    public void check(RefPermission perm) throws AuthException, PermissionBackendException {
      if (!can(perm)) {
        throw new AuthException(perm.describeForException() + " not permitted for " + refName);
      }
    }

    @Override
    public Set<RefPermission> test(Collection<RefPermission> permSet)
        throws PermissionBackendException {
      EnumSet<RefPermission> ok = EnumSet.noneOf(RefPermission.class);
      for (RefPermission perm : permSet) {
        if (can(perm)) {
          ok.add(perm);
        }
      }
      return ok;
    }

    private boolean can(RefPermission perm) throws PermissionBackendException {
      switch (perm) {
        case READ:
          return isVisible() && getProjectControl().getProjectState().statePermitsRead();
        case CREATE:
          // TODO This isn't an accurate test.
          return canPerform(perm.permissionName().get());
        case DELETE:
          return canDelete();
        case UPDATE:
          return canUpdate();
        case FORCE_UPDATE:
          return canForceUpdate();
        case SET_HEAD:
          return projectControl.isOwner();

        case FORGE_AUTHOR:
          return canForgeAuthor();
        case FORGE_COMMITTER:
          return canForgeCommitter();
        case FORGE_SERVER:
          return canForgeGerritServerIdentity();
        case MERGE:
          return canUploadMerges();

        case CREATE_CHANGE:
          return canUpload();

        case CREATE_TAG:
          return canPerform(Permission.CREATE_TAG);

        case UPDATE_BY_SUBMIT:
          return projectControl.controlForRef(MagicBranch.NEW_CHANGE + refName).canSubmit(true);

        case READ_PRIVATE_CHANGES:
          return canPerform(Permission.VIEW_PRIVATE_CHANGES);

        case READ_CONFIG:
          return projectControl
              .controlForRef(RefNames.REFS_CONFIG)
              .canPerform(RefPermission.READ.name());
        case WRITE_CONFIG:
          return isOwner();

        case SKIP_VALIDATION:
          return canForgeAuthor()
              && canForgeCommitter()
              && canForgeGerritServerIdentity()
              && canUploadMerges()
              && !projectControl.getProjectState().is(BooleanProjectConfig.USE_SIGNED_OFF_BY);
      }
      throw new PermissionBackendException(perm + " unsupported");
    }
  }
}