// src/layout/layout-persistence.ts
import {
  createInitialLayoutState,
  type LayoutState,
  type EditorMode,
  type SidebarMode,
  MIN_SIDEBAR_WIDTH,
  MAX_SIDEBAR_WIDTH,
  MIN_RIGHT_PANEL_WIDTH,
  MAX_RIGHT_PANEL_WIDTH,
} from './layout-state'

export const LAYOUT_STORAGE_KEY = 'reams:layout'
export const WORKSPACE_TABS_STORAGE_KEY = 'reams:workspace-tabs'
export const LAYOUT_VERSION = 5

interface PersistedLayoutState {
  version: number
  sidebarWidth?: number
  sidebarMode?: string
  rightPanelWidth?: number
  rightPanelCollapsed?: boolean
  editorMode?: string
}

/**
 * Save layout state to localStorage.
 * Silently fails if localStorage is unavailable.
 *
 * v5+ does not persist tab state — tabs are owned by the workspace and
 * persisted under WORKSPACE_TABS_STORAGE_KEY.
 */
export function saveLayoutState(state: LayoutState, options?: { persistEditorMode?: boolean }): void {
  try {
    const persisted: PersistedLayoutState = {
      version: LAYOUT_VERSION,
      sidebarWidth: state.sidebarWidth,
      sidebarMode: state.sidebarMode,
      rightPanelWidth: state.rightPanelWidth,
      rightPanelCollapsed: state.rightPanelCollapsed,
      ...(options?.persistEditorMode === false ? {} : { editorMode: state.editorMode }),
    }
    localStorage.setItem(LAYOUT_STORAGE_KEY, JSON.stringify(persisted))
  } catch {
    // localStorage may be unavailable (private browsing, storage full, etc.)
    // Silently fail — layout state is non-critical
  }
}

/**
 * Load layout state from localStorage.
 * Returns default state if localStorage is unavailable, empty, or invalid.
 *
 * Older layout schemas are ignored; the workspace owns tab state.
 */
export function loadLayoutState(): LayoutState {
  const defaults = createInitialLayoutState()

  try {
    const stored = localStorage.getItem(LAYOUT_STORAGE_KEY)
    if (!stored) {
      return defaults
    }

    const parsed: unknown = JSON.parse(stored)
    if (!isObject(parsed)) {
      return defaults
    }

    const persisted = parsed as unknown as PersistedLayoutState

    // Reject obsolete and unknown versions.
    if (persisted.version !== LAYOUT_VERSION) {
      return defaults
    }

    // Load v5 state.
    return {
      sidebarWidth: clampNumber(persisted.sidebarWidth, MIN_SIDEBAR_WIDTH, MAX_SIDEBAR_WIDTH, defaults.sidebarWidth),
      sidebarMode: validateSidebarMode(persisted.sidebarMode, defaults.sidebarMode),
      rightPanelWidth: clampNumber(persisted.rightPanelWidth, MIN_RIGHT_PANEL_WIDTH, MAX_RIGHT_PANEL_WIDTH, defaults.rightPanelWidth),
      rightPanelCollapsed: typeof persisted.rightPanelCollapsed === 'boolean' ? persisted.rightPanelCollapsed : defaults.rightPanelCollapsed,
      editorMode: validateEditorMode(persisted.editorMode),
    }
  } catch {
    // JSON parse error or localStorage access error
    return defaults
  }
}

function isObject(value: unknown): value is Record<string, unknown> {
  return typeof value === 'object' && value !== null && !Array.isArray(value)
}

function clampNumber(
  value: unknown,
  min: number,
  max: number,
  defaultValue: number
): number {
  if (typeof value !== 'number' || !Number.isFinite(value)) {
    return defaultValue
  }
  return Math.max(min, Math.min(max, value))
}

function validateEditorMode(mode: unknown): EditorMode {
  if (mode === 'source' || mode === 'live-preview') {
    return mode
  }
  return 'live-preview'
}

function validateSidebarMode(mode: unknown, fallback: SidebarMode): SidebarMode {
  if (mode === 'hidden' || mode === 'ribbon' || mode === 'full') {
    return mode
  }
  return fallback
}

// ============================================================================
// Workspace tab persistence (v5+)
// ============================================================================

export interface WorkspaceTabsState {
  tabs: Array<{ docUrl: string }>
  activeIndex: number
}

/**
 * Save workspace tab state to localStorage.
 * Silently fails if localStorage is unavailable.
 */
export function saveWorkspaceTabs(state: WorkspaceTabsState, storageKey = WORKSPACE_TABS_STORAGE_KEY): void {
  try {
    localStorage.setItem(storageKey, JSON.stringify(state))
  } catch {
    // Silent fail
  }
}

/**
 * Load workspace tab state from localStorage.
 * Returns null if unavailable, empty, or invalid.
 */
export function loadWorkspaceTabs(storageKey = WORKSPACE_TABS_STORAGE_KEY): WorkspaceTabsState | null {
  try {
    const stored = localStorage.getItem(storageKey)
    if (!stored) return null
    const parsed = JSON.parse(stored)
    if (!Array.isArray(parsed.tabs)) return null
    // Validate shape — filter out invalid entries
    const validTabs = parsed.tabs.filter(
      (t: unknown) => typeof t === 'object' && t !== null && typeof (t as { docUrl?: unknown }).docUrl === 'string'
    )
    return {
      tabs: validTabs,
      activeIndex: typeof parsed.activeIndex === 'number' ? parsed.activeIndex : 0,
    }
  } catch {
    return null
  }
}