import Lean.Data.Json
import Lean.Environment

import Pantograph.Version
import Pantograph.Library
import Pantograph

-- Main IO functions
open Pantograph

/-- Parse a command either in `{ "cmd": ..., "payload": ... }` form or `cmd { ... }` form. -/
def parseCommand (s: String): Except String Protocol.Command := do
  let s := s.trim
  match s.get? 0 with
  | .some '{' => -- Parse in Json mode
    Lean.fromJson? (← Lean.Json.parse s)
  | .some _ => -- Parse in line mode
    let offset := s.posOf ' ' |> s.offsetOfPos
    if offset = s.length then
      return { cmd := s.take offset, payload := Lean.Json.null }
    else
      let payload ← s.drop offset |> Lean.Json.parse
      return { cmd := s.take offset, payload := payload }
  | .none => throw "Command is empty"

partial def loop : MainM Unit := do
  let state ← get
  let command ← (← IO.getStdin).getLine
  if command.trim.length = 0 then return ()
  match parseCommand command with
  | .error error =>
    let error  := Lean.toJson ({ error := "command", desc := error }: Protocol.InteractionError)
    -- Using `Lean.Json.compress` here to prevent newline
    IO.println error.compress
  | .ok command =>
    let ret ← execute command
    let str := match state.options.printJsonPretty with
      | true => ret.pretty
      | false => ret.compress
    IO.println str
  loop


unsafe def main (args: List String): IO Unit := do
  -- NOTE: A more sophisticated scheme of command line argument handling is needed.
  -- Separate imports and options
  if args == ["--version"] then do
    println! s!"{version}"
    return

  Lean.enableInitializersExecution
  Lean.initSearchPath (← Lean.findSysroot)

  let coreContext ← args.filterMap (λ s => if s.startsWith "--" then .some <| s.drop 2 else .none)
    |>.toArray |> createCoreContext
  let imports:= args.filter (λ s => ¬ (s.startsWith "--"))
  let coreState ← createCoreState imports.toArray
  let context: Context := {
    imports
  }
  try
    let coreM := loop.run context |>.run' {}
    IO.println "ready."
    discard <| coreM.toIO coreContext coreState
  catch ex =>
    IO.println "Uncaught IO exception"
    IO.println ex.toString