Feature: Copy-on-write sandbox lifecycle
  As a developer
  I want a sandbox that isolates plan changes in a directory copy
  So that the original directory is unmodified until changes are committed

  Background:
    Given a cow test directory is initialised

  # --- Creation ---

  Scenario: Create a copy-on-write sandbox
    When a cow sandbox is created for plan "plan-001"
    Then the cow sandbox should be in the "created" state
    And the cow sandbox context should reference plan "plan-001"
    And the cow sandbox context should have strategy metadata "copy_on_write"
    And the cow sandbox path should exist

  Scenario: Creating a sandbox with empty plan_id raises ValueError
    When a cow sandbox is created with empty plan_id
    Then a cow ValueError should be raised with message "plan_id cannot be empty"

  Scenario: Creating a sandbox with empty resource_id raises ValueError
    When a cow sandbox is prepared with empty resource_id
    Then a cow ValueError should be raised with message "resource_id cannot be empty"

  Scenario: Creating a sandbox with empty original_path raises ValueError
    When a cow sandbox is prepared with empty original_path
    Then a cow ValueError should be raised with message "original_path cannot be empty"

  Scenario: Creating a sandbox on a non-existent directory raises SandboxCreationError
    Given a cow non-existent directory
    When a cow sandbox is created on the non-existent directory for plan "plan-001"
    Then a cow SandboxCreationError should be raised

  # --- Path resolution ---

  Scenario: Resolve a path in the sandbox copy
    When a cow sandbox is created for plan "plan-001"
    And the cow path "data/file.txt" is resolved
    Then the cow resolved path should be inside the sandbox copy
    And the cow sandbox should be in the "active" state

  Scenario: Path traversal is rejected
    When a cow sandbox is created for plan "plan-001"
    And the cow path "../etc/passwd" is resolved
    Then a cow ValueError should be raised with message "Path traversal not allowed"

  Scenario: Resolving a path on a cleaned-up sandbox raises SandboxStateError
    When a cow sandbox is created for plan "plan-001"
    And the cow sandbox is cleaned up
    And the cow path "file.txt" is resolved on a cleaned-up sandbox
    Then a cow SandboxStateError should be raised

  # --- Commit ---

  Scenario: Commit with no changes produces empty result
    When a cow sandbox is created for plan "plan-001"
    And the cow sandbox is committed
    Then the cow commit result should indicate success
    And the cow commit result should have 0 changed files
    And the cow commit result should have 0 added files
    And the cow commit result should have 0 deleted files

  Scenario: Commit with a new file syncs it to original
    When a cow sandbox is created for plan "plan-001"
    And a cow file "new_file.txt" is created in the sandbox with content "hello world"
    And the cow sandbox is committed
    Then the cow commit result should indicate success
    And the cow commit result should have 1 added files
    And the cow file "new_file.txt" should exist in the original directory with content "hello world"

  Scenario: Commit with a modified file syncs the change
    When a cow sandbox is created for plan "plan-001"
    And the cow existing file "existing.txt" is modified in the sandbox with content "updated"
    And the cow sandbox is committed
    Then the cow commit result should indicate success
    And the cow commit result should have 1 changed files
    And the cow file "existing.txt" in the original should have content "updated"

  Scenario: Commit with a deleted file removes it from original
    When a cow sandbox is created for plan "plan-001"
    And the cow existing file "existing.txt" is deleted from the sandbox
    And the cow sandbox is committed
    Then the cow commit result should indicate success
    And the cow commit result should have 1 deleted files
    And the cow file "existing.txt" should not exist in the original directory

  Scenario: Commit on a cleaned-up sandbox raises SandboxStateError
    When a cow sandbox is created for plan "plan-001"
    And the cow sandbox is cleaned up
    And the cow sandbox commit is attempted on cleaned-up sandbox
    Then a cow SandboxStateError should be raised

  # --- Rollback ---

  Scenario: Rollback restores the sandbox to original state
    When a cow sandbox is created for plan "plan-001"
    And a cow file "temp.txt" is created in the sandbox with content "temporary"
    And the cow path "temp.txt" is resolved
    And the cow sandbox is rolled back
    Then the cow sandbox should be in the "rolled_back" state
    And the cow file "temp.txt" should not exist in the sandbox

  Scenario: Rollback on a non-active sandbox raises SandboxStateError
    When a cow sandbox is created for plan "plan-001"
    And the cow sandbox rollback is attempted on created sandbox
    Then a cow SandboxStateError should be raised

  # --- Cleanup ---

  Scenario: Cleanup removes the sandbox directory
    When a cow sandbox is created for plan "plan-001"
    And the cow sandbox is cleaned up
    Then the cow sandbox should be in the "cleaned_up" state
    And the cow sandbox path should not exist

  Scenario: Cleanup is idempotent
    When a cow sandbox is created for plan "plan-001"
    And the cow sandbox is cleaned up
    And the cow sandbox is cleaned up again
    Then the cow sandbox should be in the "cleaned_up" state

  # --- Protocol properties ---

  Scenario: Sandbox has a unique ULID identifier
    When a cow sandbox is instantiated
    Then the cow sandbox_id should be a valid ULID
    And the cow sandbox status should be "pending"
    And the cow sandbox context should be None

  # --- Diff computation ---

  Scenario: Diff detects added, modified, and deleted files
    When a cow sandbox is created for plan "plan-001"
    And a cow file "added.txt" is created in the sandbox with content "new"
    And the cow existing file "existing.txt" is modified in the sandbox with content "changed"
    And the cow existing file "to_delete.txt" is deleted from the sandbox
    And the cow sandbox is committed
    Then the cow commit result should have 1 added files
    And the cow commit result should have 1 changed files
    And the cow commit result should have 1 deleted files