import type { StarlightUserConfig } from '@astrojs/starlight/types'

interface CommonSidebarLinkInput {
  label?: string
  attrs?: Record<string, any>
  badge?: any
  translations?: Record<string, string>
  icon?: string
}

export type SidebarLinkInput = CommonSidebarLinkInput & ({ link: string, slug?: never } | { link?: never, slug: string })

export interface SidebarManualGroupInput {
  label: string
  collapsed?: boolean
  badge?: any
  translations?: Record<string, string>
  items: SidebarInput[]
}

export interface SidebarAutogeneratedGroupInput {
  label: string
  collapsed?: boolean
  badge?: any
  translations?: Record<string, string>
  autogenerate: {
    directory: string
    collapsed?: boolean
    attrs?: Record<string, any>
  }
}

export interface SidebarLabelInput {
  label: string
  icon?: string
  badge?: any
  translations?: Record<string, string>
  attrs?: Record<string, any>
}

export type SidebarInput
  = | string
    | SidebarLinkInput
    | SidebarManualGroupInput
    | SidebarAutogeneratedGroupInput
    | SidebarLabelInput

export type StarlightSidebar = NonNullable<StarlightUserConfig['sidebar']>

/**
 * Add icons to Starlight sidebar entries by mapping a friendly `icon` property
 * to `attrs["data-icon"]`, which is consumed by the overridden Sidebar component.
 * Keeps unknown fields intact and preserves the original structure.
 *
 * The function is intentionally generic to preserve the caller's type (e.g. Starlight's
 * own sidebar item types) and avoid narrowing to the helper's local types.
 */
export function withSidebarIcons<T>(sidebar: T[]): T[] {
  return (sidebar as any[]).map((entry) => {
    if (typeof entry === 'string')
      return entry as T

    if (entry && typeof entry === 'object' && 'items' in (entry as any)) {
      const group: any = { ...(entry as any) }
      group.items = withSidebarIcons(group.items)
      return group as T
    }

    if (entry && typeof entry === 'object' && 'autogenerate' in (entry as any)) {
      return entry as T
    }

    if (entry && typeof entry === 'object') {
      const link: any = { ...(entry as any) }

      const hasLink = 'link' in link || 'slug' in link

      if (!hasLink) {
        if (typeof link.label !== 'string') {
          throw new TypeError('[starlight-plugin-icons] Sidebar item is invalid. Label-only entries require a string `label`.')
        }

        // Label-only entries are represented as `link: '#'`
        // and flagged for custom rendering in the overridden sidebar component.
        link.link = '#'
        link.attrs = { ...(link.attrs || {}), 'data-spi-label': 'true' }
      }

      const icon = link.icon as string | undefined
      if (icon) {
        const attrs = { ...(link.attrs || {}) }
        attrs['data-icon'] = icon
        delete link.icon
        link.attrs = attrs
      }
      return link as T
    }

    return entry as T
  })
}

export function defineSidebar(sidebar: SidebarInput[]): StarlightSidebar {
  return withSidebarIcons(sidebar as unknown[]) as StarlightSidebar
}