import { existsSync, readFileSync } from "fs"
import { join } from "path"
import { homedir } from "os"
import { BUILTIN_SERVERS, EXT_TO_LANG } from "./constants"

export interface ResolvedServer {
  id: string
  command: string[]
  extensions: string[]
  priority: number
  env?: Record<string, string>
  initialization?: Record<string, unknown>
}

interface LspEntry {
  disabled?: boolean
  command?: string[]
  extensions?: string[]
  priority?: number
  env?: Record<string, string>
  initialization?: Record<string, unknown>
}

interface ConfigJson {
  lsp?: Record<string, LspEntry>
}

type ConfigSource = "project" | "user" | "opencode"

interface ServerWithSource extends ResolvedServer {
  source: ConfigSource
}

function loadJsonFile<T>(path: string): T | null {
  if (!existsSync(path)) return null
  try {
    return JSON.parse(readFileSync(path, "utf-8")) as T
  } catch {
    return null
  }
}

function getConfigPaths(): { project: string; user: string; opencode: string } {
  const cwd = process.cwd()
  return {
    project: join(cwd, ".opencode", "oh-my-opencode.json"),
    user: join(homedir(), ".config", "opencode", "oh-my-opencode.json"),
    opencode: join(homedir(), ".config", "opencode", "opencode.json"),
  }
}

function loadAllConfigs(): Map<ConfigSource, ConfigJson> {
  const paths = getConfigPaths()
  const configs = new Map<ConfigSource, ConfigJson>()

  const project = loadJsonFile<ConfigJson>(paths.project)
  if (project) configs.set("project", project)

  const user = loadJsonFile<ConfigJson>(paths.user)
  if (user) configs.set("user", user)

  const opencode = loadJsonFile<ConfigJson>(paths.opencode)
  if (opencode) configs.set("opencode", opencode)

  return configs
}

function getMergedServers(): ServerWithSource[] {
  const configs = loadAllConfigs()
  const servers: ServerWithSource[] = []
  const disabled = new Set<string>()
  const seen = new Set<string>()

  const sources: ConfigSource[] = ["project", "user", "opencode"]

  for (const source of sources) {
    const config = configs.get(source)
    if (!config?.lsp) continue

    for (const [id, entry] of Object.entries(config.lsp)) {
      if (entry.disabled) {
        disabled.add(id)
        continue
      }

      if (seen.has(id)) continue
      if (!entry.command || !entry.extensions) continue

      servers.push({
        id,
        command: entry.command,
        extensions: entry.extensions,
        priority: entry.priority ?? 0,
        env: entry.env,
        initialization: entry.initialization,
        source,
      })
      seen.add(id)
    }
  }

  for (const [id, config] of Object.entries(BUILTIN_SERVERS)) {
    if (disabled.has(id) || seen.has(id)) continue

    servers.push({
      id,
      command: config.command,
      extensions: config.extensions,
      priority: -100,
      source: "opencode",
    })
  }

  return servers.sort((a, b) => {
    if (a.source !== b.source) {
      const order: Record<ConfigSource, number> = { project: 0, user: 1, opencode: 2 }
      return order[a.source] - order[b.source]
    }
    return b.priority - a.priority
  })
}

export function findServerForExtension(ext: string): ResolvedServer | null {
  const servers = getMergedServers()

  for (const server of servers) {
    if (server.extensions.includes(ext) && isServerInstalled(server.command)) {
      return {
        id: server.id,
        command: server.command,
        extensions: server.extensions,
        priority: server.priority,
        env: server.env,
        initialization: server.initialization,
      }
    }
  }

  return null
}

export function getLanguageId(ext: string): string {
  return EXT_TO_LANG[ext] || "plaintext"
}

export function isServerInstalled(command: string[]): boolean {
  if (command.length === 0) return false

  const cmd = command[0]
  const pathEnv = process.env.PATH || ""
  const paths = pathEnv.split(":")

  for (const p of paths) {
    if (existsSync(join(p, cmd))) {
      return true
    }
  }

  return false
}

export function getAllServers(): Array<{
  id: string
  installed: boolean
  extensions: string[]
  disabled: boolean
  source: string
  priority: number
}> {
  const configs = loadAllConfigs()
  const servers = getMergedServers()
  const disabled = new Set<string>()

  for (const config of configs.values()) {
    if (!config.lsp) continue
    for (const [id, entry] of Object.entries(config.lsp)) {
      if (entry.disabled) disabled.add(id)
    }
  }

  const result: Array<{
    id: string
    installed: boolean
    extensions: string[]
    disabled: boolean
    source: string
    priority: number
  }> = []

  const seen = new Set<string>()

  for (const server of servers) {
    if (seen.has(server.id)) continue
    result.push({
      id: server.id,
      installed: isServerInstalled(server.command),
      extensions: server.extensions,
      disabled: false,
      source: server.source,
      priority: server.priority,
    })
    seen.add(server.id)
  }

  for (const id of disabled) {
    if (seen.has(id)) continue
    const builtin = BUILTIN_SERVERS[id]
    result.push({
      id,
      installed: builtin ? isServerInstalled(builtin.command) : false,
      extensions: builtin?.extensions || [],
      disabled: true,
      source: "disabled",
      priority: 0,
    })
  }

  return result
}

export function getConfigPaths_(): { project: string; user: string; opencode: string } {
  return getConfigPaths()
}
