diff --git a/packages/common/src/IComment.ts b/packages/common/src/IComment.ts
index 9251630..5773b8d 100644
--- a/packages/common/src/IComment.ts
+++ b/packages/common/src/IComment.ts
@@ -2,7 +2,9 @@ export interface IComment {
   id: number
   storyId: number
   message: string
-  score: number
+  votes: number
+  spams: number
   parentId: number
-  children: IComment[]
+  userId: number
+  childrenIds?: number[]
 }
diff --git a/packages/server/src/entities/Comment.ts b/packages/server/src/entities/Comment.ts
index 484b130..dc03cd0 100644
--- a/packages/server/src/entities/Comment.ts
+++ b/packages/server/src/entities/Comment.ts
@@ -1,4 +1,4 @@
-import {Column, Entity, ManyToOne} from 'typeorm'
+import {Column, Entity, Index, ManyToOne} from 'typeorm'
 import {User} from './User'
 import {Story} from './Story'
 import {BaseEntity} from './BaseEntity'
@@ -12,6 +12,7 @@ export class Comment extends BaseEntity {
   story?: Story
 
   @Column()
+  @Index()
   storyId!: number
 
   @ManyToOne(type => User, user => user.comments)
diff --git a/packages/server/src/services/CommentService.ts b/packages/server/src/services/CommentService.ts
index 249b399..b3d2ca8 100644
--- a/packages/server/src/services/CommentService.ts
+++ b/packages/server/src/services/CommentService.ts
@@ -1,34 +1,176 @@
 import {BaseService} from './BaseService'
+import {Comment} from '../entities/Comment'
+import {ICommentService, ICommentTree} from './ICommentService'
 import {IComment} from '@rondo/common'
-import {ICommentService} from'./ICommentService'
+import {Spam} from '../entities/Spam'
+import {Validator} from '../validator'
+import {Vote} from '../entities/Vote'
 
 export class CommentService extends BaseService implements ICommentService {
 
   async find(storyId: number) {
+    const comments = await this.getRepository(Comment).find({
+      where: {
+        storyId,
+      },
+    })
+
+    const commentTree: ICommentTree = {
+      rootIds: [],
+      commentsById: {},
+    }
+    comments.reduce((obj, comment) => {
+      obj[comment.id] = comment
+      const {parentId} = comment
+      if (!parentId) {
+        commentTree.rootIds.push(comment.id)
+        return obj
+      }
+      const children =
+        obj[parentId].childrenIds =
+        obj[parentId].childrenIds || []
+      children.push(comment.id)
+      return obj
+    }, commentTree.commentsById)
+
+    return commentTree
+  }
+
+  async findOne(commentId: number) {
+    return this.getRepository(Comment).findOne(commentId)
   }
 
   async saveRoot(comment: IComment, userId: number) {
+    new Validator(comment)
+    .ensure('storyId')
+    .throw()
+
+    comment.parentId = 0
+    comment.userId = userId
+    comment.votes = 0
+    comment.spams = 0
+    return this.getRepository(Comment).save(comment)
   }
 
   async save(comment: IComment, userId: number) {
+
+    comment.votes = 0
+    comment.spams = 0
+    comment.userId = userId
+
+    new Validator(comment)
+    .ensure('message')
+    .ensure('userId')
+    .ensure('storyId')
+    .ensure('parentId')
+    .throw()
+
+    return this.getRepository(Comment).save(comment)
   }
 
   async edit(comment: IComment, userId: number) {
+    new Validator(comment)
+    .ensure('id')
+    .ensure('message')
+    .throw()
+
+    await this.getRepository(Comment)
+    .update(comment.id, {
+      message: comment.message,
+      userId,
+    })
+    const editedComment = await this.findOne(comment.id)
+
+    if (!editedComment) {
+      throw new Error('Comment not found')
+    }
+    return editedComment
   }
 
   async delete(comment: IComment, userId: number) {
+    new Validator(comment)
+    .ensure('id')
+    .throw()
+
+    await this.getRepository(Comment)
+    .update({
+      id: comment.id,
+      userId,
+    }, {
+      message: '(this message has been removed by the user)',
+    })
+
+    return this.findOne(comment.id)
   }
 
   async upVote(commentId: number, userId: number) {
+    await this.getRepository(Vote)
+    .save({
+      commentId,
+      userId,
+    })
+
+    await this.getRepository(Comment)
+    .createQueryBuilder()
+    .update()
+    .where({ id: commentId })
+    .set({
+      score: () => 'score + 1',
+    })
+    .execute()
   }
 
   async deleteVote(commentId: number, userId: number) {
+    const result = await this.getRepository(Vote)
+    .delete({
+      commentId,
+      userId,
+    })
+
+    if (result.affected && result.affected === 1) {
+      await this.getRepository(Comment)
+      .createQueryBuilder()
+      .update()
+      .where({ id: commentId })
+      .set({
+        score: () => 'score - 1',
+      })
+    }
   }
 
   async markAsSpam(commentId: number, userId: number) {
+    await this.getRepository(Spam)
+    .save({
+      commentId,
+      userId,
+    })
+
+    await this.getRepository(Comment)
+    .createQueryBuilder()
+    .update()
+    .where({ id: commentId })
+    .set({
+      spams: () => 'spams + 1',
+    })
+    .execute()
   }
 
   async unmarkAsSpam(commentId: number, userId: number) {
+    const result = await this.getRepository(Spam)
+    .delete({
+      commentId,
+      userId,
+    })
+
+    if (result.affected && result.affected === 1) {
+      await this.getRepository(Comment)
+      .createQueryBuilder()
+      .update()
+      .where({ id: commentId })
+      .set({
+        spams: () => 'spams - 1',
+      })
+    }
   }
 
 }
diff --git a/packages/server/src/services/ICommentService.ts b/packages/server/src/services/ICommentService.ts
index 3655b3c..ba1bed0 100644
--- a/packages/server/src/services/ICommentService.ts
+++ b/packages/server/src/services/ICommentService.ts
@@ -1,7 +1,16 @@
 import {IComment} from '@rondo/common'
 
+export interface ICommentTree {
+  rootIds: number[],
+  commentsById: {
+    [key: number]: IComment
+  }
+}
+
 export interface ICommentService {
-  find(storyId: number): Promise<IComment>
+  find(storyId: number): Promise<ICommentTree>
+
+  findOne(commentId: number): Promise<IComment | undefined>
 
   saveRoot(comment: IComment, userId: number): Promise<IComment>
 
@@ -9,7 +18,7 @@ export interface ICommentService {
 
   edit(comment: IComment, userId: number): Promise<IComment>
 
-  delete(comment: IComment, userId: number): Promise<IComment>
+  delete(comment: IComment, userId: number): Promise<IComment | undefined>
 
   upVote(commentId: number, userId: number): Promise<void>