Implement cloud storage with quotas and compression

Problem

Implement an in-memory cloud storage service that supports multiple users, per-user storage quotas, changing quotas with eviction, and file compression/decompression.

You are given a list of queries. Each query is an array of strings where the first element is the operation name. Return an array of strings—one result per query.

Data model

• Each user has:
  • a unique userId
  • an integer capacity (maximum total size of that user’s files)
  • zero or more files
• Each file belongs to exactly one user and has:
  • fileName (string)
  • size (positive integer)
• File names are unique per user .

Operations

All operations are scoped to a user unless stated otherwise.

1) ADD_USER userId capacity

Create a new user.

• If userId already exists: return "false" .
• Otherwise: create the user with the given capacity and return "true" .

2) ADD_FILE userId fileName size

Add a new file for a user.

• If the user does not exist: return "false" .
• If a file with that name already exists for the user: return "false" .
• If adding the file would make the user’s total used size exceed the user’s capacity: return "false" .
• Otherwise add the file and return "true" .

3) GET_FILE_SIZE userId fileName

Return the size of a file.

• If the user or file does not exist: return "" (empty string).
• Otherwise return the file size as a string.

4) UPDATE_CAPACITY userId newCapacity

Update a user’s capacity. If after the update the user is over capacity, you must delete existing files until the total used size is within capacity.

Eviction rule:

• Repeatedly delete the user’s largest file.
• If multiple files tie for largest size, delete the one with the lexicographically largest fileName to make the behavior deterministic.
• Stop once total used size $\le$ newCapacity .

Return:

• If the user does not exist: return "-1" .
• Otherwise return the number of files deleted (as a string). (If no deletion needed, return "0" .)

5) COMPRESS_FILE userId fileName

Compress an existing file.

• Compression renames the file from fileName to fileName + ".compressed" .
• The compressed file size becomes size / 2 using integer division .

Rules:

• If user does not exist: return "false" .
• If fileName does not exist: return "false" .
• If fileName already ends with .compressed : return "false" .
• If the target name fileName + ".compressed" already exists for that user: return "false" .
• Otherwise perform the rename and size change and return "true" .

Note: Compression reduces used space, so it will never violate capacity.

6) DECOMPRESS_FILE userId compressedName

Decompress an existing compressed file.

• Decompression renames compressedName to the original name by removing the .compressed suffix.
• The decompressed file size becomes size * 2 .

Rules:

• If user does not exist: return "false" .
• If compressedName does not exist: return "false" .
• If compressedName does not end with .compressed : return "false" .
• Let originalName be compressedName with the final .compressed removed. If a file named originalName already exists: return "false" .
• If decompressing would make the user exceed capacity: return "false" (and do not change anything).
• Otherwise perform the rename and size change and return "true" .

Input/Output format

• Input: queries , a list of string arrays.
• Output: list of strings, one per query.

Constraints (you may assume)

• Number of queries up to ~10^5.
• File sizes and capacities fit in 32-bit signed integers.
• userId and fileName are non-empty strings.

Example (illustrative)

Queries:

• ["ADD_USER","alice","10"] → "true"
• ["ADD_FILE","alice","a.txt","6"] → "true"
• ["COMPRESS_FILE","alice","a.txt"] → "true" (now a.txt.compressed size 3)
• ["DECOMPRESS_FILE","alice","a.txt.compressed"] → "true" (back to size 6)
• ["UPDATE_CAPACITY","alice","4"] → must delete largest files until used $\le 4$ ; return number deleted.