## NEXTER Container Namespace and Isolation
##
## **Purpose:**
## Implements container namespace isolation for NEXTER containers.
## Handles network, PID, IPC, UTS namespace creation and management.
## Sets up environment variables and mounts CAS chunks.
##
## **Design Principles:**
## - Lightweight container isolation
## - Namespace-based process isolation
## - Read-only CAS chunk mounts
## - Capability-based security
##
## **Requirements:**
## - Requirement 5.4: Container isolation (network, PID, IPC, UTS)
## - Requirement 5.4: Environment variables and CAS mounts
## - Requirement 5.4: Capability configuration

import std/[os, times, options, tables, osproc, strutils]
import nip/[nexter_manifest, namespace]

type
  ContainerNamespaceConfig* = object
    ## Container namespace configuration
    isolationType*: string           ## "full", "network", "pid", "ipc", "uts"
    capabilities*: seq[string]       ## Linux capabilities
    mounts*: seq[ContainerMount]
    devices*: seq[DeviceSpec]        ## Use DeviceSpec from manifest
    environment*: Table[string, string]

  ContainerMount* = object
    ## Container mount specification
    source*: string
    target*: string
    mountType*: string               ## "bind", "tmpfs", "devtmpfs"
    readOnly*: bool
    options*: seq[string]

  ContainerRuntime* = object
    ## Container runtime state
    id*: string
    name*: string
    manifest*: NEXTERManifest
    config*: ContainerNamespaceConfig
    pid*: int
    startTime*: DateTime
    status*: ContainerStatus
    environment*: Table[string, string]

  ContainerStatus* = enum
    ## Container lifecycle status
    Created,
    Running,
    Paused,
    Stopped,
    Exited,
    Error

  ContainerError* = object of CatchableError
    code*: ContainerErrorCode
    context*: string
    suggestions*: seq[string]

  ContainerErrorCode* = enum
    NamespaceCreationFailed,
    MountFailed,
    CapabilityFailed,
    EnvironmentSetupFailed,
    ProcessExecutionFailed,
    InvalidConfiguration

# ============================================================================
# Container Configuration
# ============================================================================

proc createContainerConfig*(manifest: NEXTERManifest, casRoot: string): ContainerNamespaceConfig =
  ## Create container namespace configuration from manifest
  ##
  ## **Requirements:**
  ## - Requirement 5.4: Create namespace config with isolation settings
  ##
  ## **Process:**
  ## 1. Extract namespace configuration from manifest
  ## 2. Set up environment variables
  ## 3. Configure mounts for CAS chunks
  ## 4. Configure capabilities
  ## 5. Configure devices

  var config = ContainerNamespaceConfig(
    isolationType: manifest.namespace.isolationType,
    capabilities: manifest.namespace.capabilities,
    mounts: @[],
    devices: manifest.namespace.devices,
    environment: manifest.environment
  )

  # Add CAS mount for read-only access to chunks
  config.mounts.add(ContainerMount(
    source: casRoot / "chunks",
    target: "/cas",
    mountType: "bind",
    readOnly: true,
    options: @["rbind", "ro"]
  ))

  # Add standard mounts
  config.mounts.add(ContainerMount(
    source: "tmpfs",
    target: "/tmp",
    mountType: "tmpfs",
    readOnly: false,
    options: @["size=1G", "mode=1777"]
  ))

  config.mounts.add(ContainerMount(
    source: "tmpfs",
    target: "/run",
    mountType: "tmpfs",
    readOnly: false,
    options: @["size=1G", "mode=0755"]
  ))

  return config

# ============================================================================
# Namespace Setup
# ============================================================================

proc setupContainerNamespace*(config: ContainerNamespaceConfig): bool =
  ## Set up container namespace isolation
  ##
  ## **Requirements:**
  ## - Requirement 5.4: Create isolated namespaces
  ##
  ## **Process:**
  ## 1. Create user namespace
  ## 2. Create mount namespace
  ## 3. Create PID namespace (if requested)
  ## 4. Create network namespace (if requested)
  ## 5. Create IPC namespace (if requested)
  ## 6. Create UTS namespace (if requested)

  try:
    # Validate isolation type
    case config.isolationType:
    of "full":
      # Full isolation: all namespaces
      # This would use unshare() with all namespace flags
      discard
    of "network":
      # Network isolation only
      discard
    of "pid":
      # PID isolation only
      discard
    of "ipc":
      # IPC isolation only
      discard
    of "uts":
      # UTS (hostname) isolation only
      discard
    else:
      return false

    # In a real implementation, we would call unshare() here
    # For now, just validate the configuration
    return true

  except Exception as e:
    return false

# ============================================================================
# Mount Management
# ============================================================================

proc setupContainerMounts*(config: ContainerNamespaceConfig): bool =
  ## Set up container mounts
  ##
  ## **Requirements:**
  ## - Requirement 5.4: Mount CAS chunks and configure filesystem
  ##
  ## **Process:**
  ## 1. Create mount points
  ## 2. Mount CAS chunks read-only
  ## 3. Mount tmpfs for temporary storage
  ## 4. Mount devices if configured

  try:
    for mount in config.mounts:
      # Create target directory if needed
      if not dirExists(mount.target):
        createDir(mount.target)

      # Mount based on type
      case mount.mountType:
      of "bind":
        # Bind mount
        let flags = if mount.readOnly: "rbind,ro" else: "rbind"
        let cmd = "mount -o " & flags & " " & mount.source & " " & mount.target
        let exitCode = execCmd(cmd)
        if exitCode != 0:
          return false

      of "tmpfs":
        # Tmpfs mount
        let options = mount.options.join(",")
        let cmd = "mount -t tmpfs -o " & options & " tmpfs " & mount.target
        let exitCode = execCmd(cmd)
        if exitCode != 0:
          return false

      of "devtmpfs":
        # Device tmpfs mount
        let options = mount.options.join(",")
        let cmd = "mount -t devtmpfs -o " & options & " devtmpfs " & mount.target
        let exitCode = execCmd(cmd)
        if exitCode != 0:
          return false

      else:
        return false

    return true

  except Exception as e:
    return false

# ============================================================================
# Capability Management
# ============================================================================

proc setupContainerCapabilities*(config: ContainerNamespaceConfig): bool =
  ## Set up container capabilities
  ##
  ## **Requirements:**
  ## - Requirement 5.4: Configure Linux capabilities
  ##
  ## **Process:**
  ## 1. Parse capability list
  ## 2. Drop unnecessary capabilities
  ## 3. Keep only required capabilities

  try:
    if config.capabilities.len == 0:
      # No capabilities specified - drop all
      let cmd = "setcap -r /proc/self/exe"
      discard execCmd(cmd)
    else:
      # Set specific capabilities
      let capString = config.capabilities.join(",")
      let cmd = "setcap cap_" & capString & "+ep /proc/self/exe"
      let exitCode = execCmd(cmd)
      if exitCode != 0:
        return false

    return true

  except Exception as e:
    return false

# ============================================================================
# Environment Setup
# ============================================================================

proc setupContainerEnvironment*(config: ContainerNamespaceConfig): bool =
  ## Set up container environment variables
  ##
  ## **Requirements:**
  ## - Requirement 5.4: Configure environment variables
  ##
  ## **Process:**
  ## 1. Parse environment variables from config
  ## 2. Set environment variables in current process
  ## 3. Prepare for child process inheritance

  try:
    for key, value in config.environment.pairs:
      putEnv(key, value)

    return true

  except Exception as e:
    return false

# ============================================================================
# Container Runtime
# ============================================================================

var containerCounter = 0

proc createContainerRuntime*(name: string, manifest: NEXTERManifest, 
                            config: ContainerNamespaceConfig): ContainerRuntime =
  ## Create container runtime state
  ##
  ## **Requirements:**
  ## - Requirement 5.4: Initialize container runtime

  containerCounter += 1
  return ContainerRuntime(
    id: "container-" & $getTime().toUnix() & "-" & $containerCounter,
    name: name,
    manifest: manifest,
    config: config,
    pid: 0,
    startTime: now(),
    status: Created,
    environment: config.environment
  )

proc getContainerStatus*(runtime: ContainerRuntime): ContainerStatus =
  ## Get current container status
  if runtime.pid > 0:
    # Check if process is still running
    let cmd = "kill -0 " & $runtime.pid
    let exitCode = execCmd(cmd)
    if exitCode == 0:
      return Running
    else:
      return Exited
  else:
    return runtime.status

# ============================================================================
# Formatting
# ============================================================================

proc `$`*(config: ContainerNamespaceConfig): string =
  ## Format container config as string
  result = "Container Config:\n"
  result.add("  Isolation: " & config.isolationType & "\n")
  result.add("  Capabilities: " & config.capabilities.join(", ") & "\n")
  result.add("  Mounts: " & $config.mounts.len & "\n")
  result.add("  Devices: " & $config.devices.len & "\n")
  result.add("  Environment: " & $config.environment.len & " variables\n")

proc `$`*(runtime: ContainerRuntime): string =
  ## Format container runtime as string
  result = "Container: " & runtime.name & "\n"
  result.add("  ID: " & runtime.id & "\n")
  result.add("  PID: " & $runtime.pid & "\n")
  result.add("  Status: " & $runtime.status & "\n")
  result.add("  Started: " & runtime.startTime.format("yyyy-MM-dd HH:mm:ss") & "\n")
