Coding Challenge #5: JSON Config Validator

Your team's microservice is crashing in production because someone deployed it with a malformed configuration file. The JSON has a missing required field, a string where a number should be, or an invalid URL format. These issues slip through manual reviews and only show up when the service tries to start.

You need a config validator that catches these problems before deployment, validates data types, checks required fields, and ensures values meet business rules (valid URLs, positive numbers, etc.).

Your Mission

Build a JSON configuration validator that reads schema definitions and validates config files against them, providing clear error messages for any violations.

Requirements

Your tool must:

• Read JSON schema definitions from a file

• Validate JSON config files against the schema

• Check for required fields and report missing ones

• Validate data types (string, number, boolean, array, object)

• Support format validation (email, URL, date patterns)

• Validate value constraints (min/max, string length, enum values)

• Generate detailed error reports with field paths and suggestions

• Exit with appropriate codes for CI/CD integration

• Support nested object and array validation

Sample Schema (app_schema.json)

{
  "type": "object",
  "required": ["database", "server", "logging"],
  "properties": {
    "database": {
      "type": "object",
      "required": ["host", "port", "name"],
      "properties": {
        "host": {
          "type": "string",
          "format": "hostname"
        },
        "port": {
          "type": "integer",
          "minimum": 1,
          "maximum": 65535
        },
        "name": {
          "type": "string",
          "minLength": 1,
          "maxLength": 50
        },
        "ssl": {
          "type": "boolean",
          "default": false
        }
      }
    },
    "server": {
      "type": "object",
      "required": ["port", "host"],
      "properties": {
        "port": {
          "type": "integer",
          "minimum": 1024,
          "maximum": 9999
        },
        "host": {
          "type": "string",
          "default": "localhost"
        },
        "workers": {
          "type": "integer",
          "minimum": 1,
          "maximum": 16,
          "default": 4
        }
      }
    },
    "logging": {
      "type": "object",
      "required": ["level"],
      "properties": {
        "level": {
          "type": "string",
          "enum": ["DEBUG", "INFO", "WARNING", "ERROR"]
        },
        "file": {
          "type": "string",
          "format": "filepath"
        },
        "max_size": {
          "type": "string",
          "pattern": "^\\d+[KMG]B$"
        }
      }
    },
    "features": {
      "type": "array",
      "items": {
        "type": "string"
      },
      "uniqueItems": true
    }
  }
}

Sample Config (app_config.json)

{
  "database": {
    "host": "db.example.com",
    "port": 5432,
    "name": "myapp_prod"
  },
  "server": {
    "port": 8080,
    "host": "0.0.0.0",
    "workers": 8
  },
  "logging": {
    "level": "INFO",
    "file": "/var/log/app.log",
    "max_size": "100MB"
  },
  "features": ["auth", "metrics", "cache"]
}

Expected Output (Valid Config)

JSON Configuration Validation Report
=====================================
📄 Schema: app_schema.json
📄 Config: app_config.json
⏱️  Validation time: 12ms

✅ Configuration is VALID

📊 Validation Summary:
======================
✅ All required fields present
✅ All data types correct
✅ All constraints satisfied
✅ No format violations

🔍 Field Analysis:
==================
database.host: ✅ Valid hostname
database.port: ✅ Valid port (5432)
database.name: ✅ Valid string (length: 10)
server.port: ✅ Valid port (8080)
server.workers: ✅ Valid range (8/16)
logging.level: ✅ Valid enum (INFO)
logging.max_size: ✅ Valid pattern (100MB)
features: ✅ Valid array (3 unique items)

Exit code: 0

Expected Output (Invalid Config)

JSON Configuration Validation Report
=====================================
📄 Schema: app_schema.json
📄 Config: invalid_config.json
⏱️  Validation time: 8ms

❌ Configuration is INVALID

🚨 Validation Errors (4 found):
================================

Error 1: Missing required field
--------------------------------
Path: database.ssl
Expected: boolean (optional with default: false)
Suggestion: Add "ssl": false to database object

Error 2: Invalid data type
---------------------------
Path: server.port
Expected: integer (1024-9999)
Actual: "8080" (string)
Suggestion: Remove quotes: "port": 8080

Error 3: Value out of range
----------------------------
Path: server.workers
Expected: integer (1-16)
Actual: 20
Suggestion: Use value between 1 and 16

Error 4: Invalid enum value
----------------------------
Path: logging.level
Expected: one of ["DEBUG", "INFO", "WARNING", "ERROR"]
Actual: "TRACE"
Suggestion: Use "DEBUG" for detailed logging

Exit code: 1 (validation failed)