{
  "openapi": "3.0.3",
  "info": {
    "title": "Chatterbox API",
    "version": "1.0.0",
    "description": "Production-grade REST & Socket.io real-time chat API specification for Chatterbox. Includes formalized request and response schemas, authentication patterns, error codes, and WebSocket events."
  },
  "servers": [
    {
      "url": "https://frontend-task-chatapp.onrender.com/api",
      "description": "Production Live API"
    }
  ],
  "security": [
    {
      "bearerAuth": []
    }
  ],
  "paths": {
    "/auth/login": {
      "post": {
        "tags": ["Auth"],
        "summary": "Log in or Auto-Register",
        "description": "Single-step authentication. If the phone number exists, returns session credentials. If the phone number is new, automatically provisions a new account.",
        "security": [],
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/LoginRequest"
              },
              "example": {
                "phone": "+19991234567",
                "name": "Alice Developer"
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Successfully authenticated",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/AuthResponse"
                }
              }
            }
          },
          "400": {
            "description": "Validation failed",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/ErrorResponse"
                }
              }
            }
          }
        }
      }
    },
    "/auth/me": {
      "get": {
        "tags": ["Auth"],
        "summary": "Get Current User Profile",
        "description": "Returns user identity matching the Bearer JWT token in Authorization header.",
        "responses": {
          "200": {
            "description": "Current user profile",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/User"
                }
              }
            }
          },
          "401": {
            "description": "Unauthorized / Invalid Token",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/ErrorResponse"
                }
              }
            }
          }
        }
      }
    },
    "/users/search": {
      "get": {
        "tags": ["Users"],
        "summary": "Search Users",
        "description": "Searches registered users by name or phone substring. Query parameter `query` or `q` is supported.",
        "parameters": [
          {
            "name": "query",
            "in": "query",
            "description": "Search query substring",
            "required": false,
            "schema": {
              "type": "string"
            }
          }
        ],
        "responses": {
          "200": {
            "description": "Matching users list",
            "content": {
              "application/json": {
                "schema": {
                  "type": "array",
                  "items": {
                    "$ref": "#/components/schemas/User"
                  }
                }
              }
            }
          },
          "401": {
            "description": "Unauthorized",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/ErrorResponse"
                }
              }
            }
          }
        }
      }
    },
    "/conversations": {
      "get": {
        "tags": ["Conversations"],
        "summary": "List Conversations",
        "description": "Fetches all direct and group conversations for the authenticated user, ordered by most recent update.",
        "responses": {
          "200": {
            "description": "List of user conversations",
            "content": {
              "application/json": {
                "schema": {
                  "type": "object",
                  "properties": {
                    "data": {
                      "type": "array",
                      "items": {
                        "$ref": "#/components/schemas/Conversation"
                      }
                    }
                  }
                }
              }
            }
          }
        }
      },
      "post": {
        "tags": ["Conversations"],
        "summary": "Start Direct Conversation",
        "description": "Creates or retrieves an existing 1-to-1 conversation with the designated user ID.",
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/StartConversationRequest"
              },
              "example": {
                "userId": "6a88601ee5d6aac97522899c"
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Existing direct conversation returned",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Conversation"
                }
              }
            }
          },
          "201": {
            "description": "New direct conversation created",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Conversation"
                }
              }
            }
          }
        }
      }
    },
    "/conversations/group": {
      "post": {
        "tags": ["Groups"],
        "summary": "Create Group Conversation",
        "description": "Creates a multi-participant group conversation (requires group name and at least 2 other participant IDs).",
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/CreateGroupRequest"
              },
              "example": {
                "name": "Avengers Core",
                "participantIds": ["6a886060e5d6aac975228aff", "6a886061e5d6aac975228b05"]
              }
            }
          }
        },
        "responses": {
          "201": {
            "description": "Group conversation created successfully",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Conversation"
                }
              }
            }
          },
          "400": {
            "description": "Validation error (less than 3 total members or missing name)"
          }
        }
      }
    },
    "/conversations/{id}": {
      "patch": {
        "tags": ["Groups"],
        "summary": "Rename Group Conversation",
        "description": "Renames a group conversation. Must be executed by a group admin.",
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "description": "Group Conversation ID",
            "schema": { "type": "string" }
          }
        ],
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/RenameGroupRequest"
              },
              "example": {
                "name": "Avengers Elite"
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Group renamed successfully",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Conversation"
                }
              }
            }
          },
          "403": {
            "description": "Forbidden (Caller is not an admin)"
          }
        }
      }
    },
    "/conversations/{id}/admins": {
      "post": {
        "tags": ["Groups"],
        "summary": "Promote Member to Admin",
        "description": "Promotes an existing participant to admin status. Requires admin permissions.",
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "description": "Group Conversation ID",
            "schema": { "type": "string" }
          }
        ],
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/PromoteRequest"
              },
              "example": {
                "userId": "6a886060e5d6aac975228aff"
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Member promoted to admin",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Conversation"
                }
              }
            }
          }
        }
      }
    },
    "/conversations/{id}/participants": {
      "post": {
        "tags": ["Groups"],
        "summary": "Add Participants to Group",
        "description": "Adds one or more users to an existing group conversation. Requires admin permissions.",
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "description": "Group Conversation ID",
            "schema": { "type": "string" }
          }
        ],
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/AddParticipantsRequest"
              },
              "example": {
                "userIds": ["6a886061e5d6aac975228b05"]
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Participants added to group",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Conversation"
                }
              }
            }
          }
        }
      }
    },
    "/conversations/{id}/participants/{userId}": {
      "delete": {
        "tags": ["Groups"],
        "summary": "Remove Participant / Leave Group",
        "description": "Removes a participant from a group (if caller is admin) or allows the caller to leave the group.",
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "description": "Group Conversation ID",
            "schema": { "type": "string" }
          },
          {
            "name": "userId",
            "in": "path",
            "required": true,
            "description": "User ID to remove",
            "schema": { "type": "string" }
          }
        ],
        "responses": {
          "200": {
            "description": "Participant removed or left successfully",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Conversation"
                }
              }
            }
          }
        }
      }
    },
    "/conversations/{id}/messages": {
      "get": {
        "tags": ["Messages"],
        "summary": "Get Message History",
        "description": "Fetches chronological message history for a direct or group conversation.",
        "parameters": [
          {
            "name": "id",
            "in": "path",
            "required": true,
            "description": "Conversation ID",
            "schema": { "type": "string" }
          }
        ],
        "responses": {
          "200": {
            "description": "Messages history list",
            "content": {
              "application/json": {
                "schema": {
                  "type": "object",
                  "properties": {
                    "messages": {
                      "type": "array",
                      "items": {
                        "$ref": "#/components/schemas/Message"
                      }
                    },
                    "hasMore": {
                      "type": "boolean"
                    }
                  }
                }
              }
            }
          }
        }
      }
    },
    "/messages": {
      "post": {
        "tags": ["Messages"],
        "summary": "Send Message",
        "description": "Dispatches a new text message to a conversation. Reconciles with optimistic dispatch on client and triggers Socket.io broadcast to peers.",
        "requestBody": {
          "required": true,
          "content": {
            "application/json": {
              "schema": {
                "$ref": "#/components/schemas/SendMessageRequest"
              },
              "example": {
                "conversationId": "6a886020e5d6aac9752289b2",
                "text": "Hello world!"
              }
            }
          }
        },
        "responses": {
          "200": {
            "description": "Message sent and persisted",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Message"
                }
              }
            }
          },
          "201": {
            "description": "Message created",
            "content": {
              "application/json": {
                "schema": {
                  "$ref": "#/components/schemas/Message"
                }
              }
            }
          }
        }
      }
    },
    "/health": {
      "get": {
        "tags": ["System"],
        "summary": "Service Health Check",
        "description": "Checks whether the backend server is operational. Hosted at root `/health`.",
        "security": [],
        "responses": {
          "200": {
            "description": "Service is healthy",
            "content": {
              "application/json": {
                "schema": {
                  "type": "object",
                  "properties": {
                    "status": { "type": "string", "example": "ok" }
                  }
                }
              }
            }
          }
        }
      }
    }
  },
  "components": {
    "securitySchemes": {
      "bearerAuth": {
        "type": "http",
        "scheme": "bearer",
        "bearerFormat": "JWT"
      }
    },
    "schemas": {
      "User": {
        "type": "object",
        "required": ["_id", "name", "phone"],
        "properties": {
          "_id": { "type": "string", "example": "6a886007e5d6aac9752288cb" },
          "name": { "type": "string", "example": "Alice Developer" },
          "phone": { "type": "string", "example": "+19991234567" },
          "createdAt": { "type": "string", "format": "date-time", "example": "2026-08-21T14:26:15.688Z" }
        }
      },
      "DirectParticipant": {
        "type": "object",
        "required": ["_id", "name", "phone"],
        "properties": {
          "_id": { "type": "string", "example": "6a88601ee5d6aac97522899c" },
          "name": { "type": "string", "example": "Bob Test" },
          "phone": { "type": "string", "example": "+1888489938" }
        }
      },
      "ConversationLastMessage": {
        "type": "object",
        "properties": {
          "text": { "type": "string", "example": "Hello Bob! How are you?" },
          "sender": { "type": "string", "example": "6a88601de5d6aac975228994" },
          "createdAt": { "type": "string", "format": "date-time", "example": "2026-08-21T14:26:41.507Z" }
        }
      },
      "Conversation": {
        "type": "object",
        "required": ["_id", "type"],
        "properties": {
          "_id": { "type": "string", "example": "6a886020e5d6aac9752289b2" },
          "type": { "type": "string", "enum": ["direct", "group"], "example": "direct" },
          "name": { "type": "string", "example": "Avengers Elite" },
          "createdBy": { "type": "string", "example": "6a886060e5d6aac975228afa" },
          "admins": { "type": "array", "items": { "type": "string" } },
          "participants": {
            "type": "array",
            "items": { "$ref": "#/components/schemas/DirectParticipant" }
          },
          "participant": { "$ref": "#/components/schemas/DirectParticipant" },
          "lastMessage": { "$ref": "#/components/schemas/ConversationLastMessage" },
          "createdAt": { "type": "string", "format": "date-time" },
          "updatedAt": { "type": "string", "format": "date-time" }
        }
      },
      "Message": {
        "type": "object",
        "required": ["_id", "conversation", "sender", "text", "createdAt"],
        "properties": {
          "_id": { "type": "string", "example": "6a886021e5d6aac9752289be" },
          "conversation": { "type": "string", "example": "6a886020e5d6aac9752289b2" },
          "sender": { "type": "string", "example": "6a88601de5d6aac975228994" },
          "text": { "type": "string", "example": "Hello Bob! How are you?" },
          "createdAt": { "type": "string", "format": "date-time", "example": "2026-08-21T14:26:41.507Z" }
        }
      },
      "LoginRequest": {
        "type": "object",
        "required": ["phone", "name"],
        "properties": {
          "phone": { "type": "string", "example": "+19991234567" },
          "name": { "type": "string", "example": "Alice Developer" }
        }
      },
      "AuthResponse": {
        "type": "object",
        "required": ["token", "user"],
        "properties": {
          "token": { "type": "string", "example": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9..." },
          "user": { "$ref": "#/components/schemas/User" }
        }
      },
      "StartConversationRequest": {
        "type": "object",
        "required": ["userId"],
        "properties": {
          "userId": { "type": "string", "example": "6a88601ee5d6aac97522899c" }
        }
      },
      "CreateGroupRequest": {
        "type": "object",
        "required": ["name", "participantIds"],
        "properties": {
          "name": { "type": "string", "example": "Avengers Team" },
          "participantIds": {
            "type": "array",
            "items": { "type": "string" },
            "example": ["6a886060e5d6aac975228aff", "6a886061e5d6aac975228b05"]
          }
        }
      },
      "RenameGroupRequest": {
        "type": "object",
        "required": ["name"],
        "properties": {
          "name": { "type": "string", "example": "Avengers Elite" }
        }
      },
      "PromoteRequest": {
        "type": "object",
        "required": ["userId"],
        "properties": {
          "userId": { "type": "string", "example": "6a886060e5d6aac975228aff" }
        }
      },
      "AddParticipantsRequest": {
        "type": "object",
        "required": ["userIds"],
        "properties": {
          "userIds": {
            "type": "array",
            "items": { "type": "string" },
            "example": ["6a886061e5d6aac975228b05"]
          }
        }
      },
      "SendMessageRequest": {
        "type": "object",
        "required": ["conversationId", "text"],
        "properties": {
          "conversationId": { "type": "string", "example": "6a886020e5d6aac9752289b2" },
          "text": { "type": "string", "example": "Hello Bob! How are you?" }
        }
      },
      "ErrorResponse": {
        "type": "object",
        "properties": {
          "error": {
            "type": "object",
            "properties": {
              "message": { "type": "string", "example": "Validation failed" },
              "code": { "type": "string", "example": "VALIDATION_ERROR" },
              "details": { "type": "array", "items": { "type": "object" } }
            }
          }
        }
      }
    }
  }
}