open Import
open Sexp.Of_sexp

module Env_var_map = Context.Env_var_map

type var_expansion =
  | Not_found
  | Path  of Path.t
  | Paths of Path.t list
  | Str   of string

let expand_str ~dir ~f template =
  String_with_vars.expand template ~f:(fun var ->
    match f var with
    | Not_found -> None
    | Path path -> Some (Path.reach ~from:dir path)
    | Paths l -> Some (List.map l ~f:(Path.reach ~from:dir) |> String.concat ~sep:" ")
    | Str s -> Some s)

let expand_path ~dir ~f template =
  match String_with_vars.just_a_var template with
  | None -> expand_str ~dir ~f template |> Path.relative dir
  | Some v ->
    match f v with
    | Not_found -> expand_str ~dir ~f template |> Path.relative dir
    | Path p
    | Paths [p] -> p
    | Str s -> Path.relative dir s
    | Paths l ->
      List.map l ~f:(Path.reach ~from:dir)
      |> String.concat ~sep:" "
      |> Path.relative dir

let expand_prog ctx ~dir ~f template =
  let resolve s =
    if String.contains s '/' then
      Path.relative dir s
    else
      match Context.which ctx s with
      | Some p -> p
      | None -> Utils.program_not_found ~context:ctx.name s
  in
  match String_with_vars.just_a_var template with
  | None -> resolve (expand_str ~dir ~f template)
  | Some v ->
    match f v with
    | Not_found -> resolve (expand_str ~dir ~f template)
    | Path p
    | Paths [p] -> p
    | Str s -> resolve s
    | Paths l ->
      List.map l ~f:(Path.reach ~from:dir)
      |> String.concat ~sep:" "
      |> resolve

module Ast = struct
  type outputs =
    | Stdout
    | Stderr
    | Outputs (* Both Stdout and Stderr *)

  let string_of_outputs = function
    | Stdout -> "stdout"
    | Stderr -> "stderr"
    | Outputs -> "outputs"

  type ('a, 'path) t =
    | Run            of 'path * 'a list
    | Chdir          of 'path * ('a, 'path) t
    | Setenv         of 'a * 'a * ('a, 'path) t
    | Redirect       of outputs * 'path * ('a, 'path) t
    | Ignore         of outputs * ('a, 'path) t
    | Progn          of ('a, 'path) t list
    | Echo           of 'a
    | Create_file    of 'path
    | Cat            of 'path
    | Copy           of 'path * 'path
    | Symlink        of 'path * 'path
    | Copy_and_add_line_directive of 'path * 'path
    | System         of 'a
    | Bash           of 'a
    | Update_file    of 'path * 'a
    | Rename         of 'path * 'path
    | Remove_tree    of 'path

  let rec t a p sexp =
    sum
      [ cstr_rest "run" (p @> nil) a             (fun prog args -> Run (prog, args))
      ; cstr "chdir"    (p @> t a p @> nil)        (fun dn t -> Chdir (dn, t))
      ; cstr "setenv"   (a @> a @> t a p @> nil)   (fun k v t -> Setenv (k, v, t))
      ; cstr "with-stdout-to"  (p @> t a p @> nil) (fun fn t -> Redirect (Stdout, fn, t))
      ; cstr "with-stderr-to"  (p @> t a p @> nil) (fun fn t -> Redirect (Stderr, fn, t))
      ; cstr "with-outputs-to" (p @> t a p @> nil) (fun fn t -> Redirect (Outputs, fn, t))
      ; cstr "ignore-stdout"   (t a p @> nil)      (fun t -> Ignore (Stdout, t))
      ; cstr "ignore-stderr"   (t a p @> nil)      (fun t -> Ignore (Stderr, t))
      ; cstr "ignore-outputs"  (t a p @> nil)      (fun t -> Ignore (Outputs, t))
      ; cstr_rest "progn"      nil (t a p)         (fun l -> Progn l)
      ; cstr "echo"           (a @> nil)         (fun x -> Echo x)
      ; cstr "cat"            (p @> nil)         (fun x -> Cat x)
      ; cstr "create-file"    (p @> nil)         (fun x -> Create_file x)
      ; cstr "copy" (p @> p @> nil)              (fun src dst -> Copy (src, dst))
      (*
         (* We don't expose symlink to the user yet since this might complicate things *)
         ; cstr "symlink" (a @> a @> nil) (fun src dst -> Symlink (dst, Cat src))
      *)
      ; cstr "copy-and-add-line-directive" (p @> p @> nil) (fun src dst ->
          Copy_and_add_line_directive (src, dst))
      ; cstr "system" (a @> nil) (fun cmd -> System cmd)
      ; cstr "bash"   (a @> nil) (fun cmd -> Bash   cmd)
      ]
      sexp

  let rec sexp_of_t f g : _ -> Sexp.t = function
    | Run (a, xs) -> List (Atom "run" :: g a :: List.map xs ~f)
    | Chdir (a, r) -> List [Atom "chdir" ; g a ; sexp_of_t f g r]
    | Setenv (k, v, r) -> List [Atom "setenv" ; f k ; f v ; sexp_of_t f g r]
    | Redirect (outputs, fn, r) ->
      List [ Atom (sprintf "with-%s-to" (string_of_outputs outputs))
           ; g fn
           ; sexp_of_t f g r
           ]
    | Ignore (outputs, r) ->
      List [ Atom (sprintf "ignore-%s" (string_of_outputs outputs))
           ; sexp_of_t f g r
           ]
    | Progn l -> List (Atom "progn" :: List.map l ~f:(sexp_of_t f g))
    | Echo x -> List [Atom "echo"; f x]
    | Cat x -> List [Atom "cat"; g x]
    | Create_file x -> List [Atom "create-file"; g x]
    | Copy (x, y) ->
      List [Atom "copy"; g x; g y]
    | Symlink (x, y) ->
      List [Atom "symlink"; g x; g y]
    | Copy_and_add_line_directive (x, y) ->
      List [Atom "copy-and-add-line-directive"; g x; g y]
    | System x -> List [Atom "system"; f x]
    | Bash   x -> List [Atom "bash"; f x]
    | Update_file (x, y) -> List [Atom "update-file"; g x; f y]
    | Rename (x, y) -> List [Atom "rename"; g x; g y]
    | Remove_tree x -> List [Atom "remove-tree"; g x]

  let rec fold t ~init:acc ~f =
    match t with
    | Run (prog, args) -> List.fold_left args ~init:(f acc prog) ~f
    | Chdir (fn, t) -> fold t ~init:(f acc fn) ~f
    | Setenv (var, value, t) -> fold t ~init:(f (f acc var) value) ~f
    | Redirect (_, fn, t) -> fold t ~init:(f acc fn) ~f
    | Ignore (_, t) -> fold t ~init:acc ~f
    | Progn l -> List.fold_left l ~init:acc ~f:(fun init t -> fold t ~init ~f)
    | Echo x -> f acc x
    | Cat x -> f acc x
    | Create_file x -> f acc x
    | Copy (x, y) -> f (f acc x) y
    | Symlink (x, y) -> f (f acc x) y
    | Copy_and_add_line_directive (x, y) -> f (f acc x) y
    | System x -> f acc x
    | Bash x -> f acc x
    | Update_file (x, y) -> f (f acc x) y
    | Rename (x, y) -> f (f acc x) y
    | Remove_tree x -> f acc x

  let fold_one_step t ~init:acc ~f =
    match t with
    | Chdir (_, t)
    | Setenv (_, _, t)
    | Redirect (_, _, t)
    | Ignore (_, t) -> f acc t
    | Progn l -> List.fold_left l ~init:acc ~f
    | Run _
    | Echo _
    | Cat _
    | Create_file _
    | Copy _
    | Symlink _
    | Copy_and_add_line_directive _
    | System _
    | Bash _
    | Update_file _
    | Rename _
    | Remove_tree _ -> acc

  let rec map
    : 'a 'b 'c 'd. ('a, 'b) t -> f1:('a -> 'c) -> f2:('b -> 'd) -> ('c, 'd) t
    = fun t ~f1 ~f2 ->
      match t with
      | Run (prog, args) ->
        Run (f2 prog, List.map args ~f:f1)
      | Chdir (fn, t) ->
        Chdir (f2 fn, map t ~f1 ~f2)
      | Setenv (var, value, t) ->
        Setenv (f1 var, f1 value, map t ~f1 ~f2)
      | Redirect (outputs, fn, t) ->
        Redirect (outputs, f2 fn, map t ~f1 ~f2)
      | Ignore (outputs, t) ->
        Ignore (outputs, map t ~f1 ~f2)
      | Progn l -> Progn (List.map l ~f:(fun t -> map t ~f1 ~f2))
      | Echo x -> Echo (f1 x)
      | Cat x -> Cat (f2 x)
      | Create_file x -> Create_file (f2 x)
      | Copy (x, y) -> Copy (f2 x, f2 y)
      | Symlink (x, y) ->
        Symlink (f2 x, f2 y)
      | Copy_and_add_line_directive (x, y) ->
        Copy_and_add_line_directive (f2 x, f2 y)
      | System x -> System (f1 x)
      | Bash x -> Bash (f1 x)
      | Update_file (x, y) -> Update_file (f2 x, f1 y)
      | Rename (x, y) -> Rename (f2 x, f2 y)
      | Remove_tree x -> Remove_tree (f2 x)
end
open Ast

type t = (string, Path.t) Ast.t
let t = Ast.t string Path.t
let sexp_of_t = Ast.sexp_of_t Sexp.To_sexp.string Path.sexp_of_t

let updated_files =
  let rec loop acc t =
    let acc =
      match t with
      | Update_file (fn, _) -> Path.Set.add fn acc
      | _ -> acc
    in
    Ast.fold_one_step t ~init:acc ~f:loop
  in
  fun t -> loop Path.Set.empty t

let chdirs =
  let rec loop acc t =
    let acc =
      match t with
      | Chdir (dir, _) -> Path.Set.add dir acc
      | _ -> acc
    in
    Ast.fold_one_step t ~init:acc ~f:loop
  in
  fun t -> loop Path.Set.empty t

module Unexpanded = struct
  type t = (String_with_vars.t, String_with_vars.t) Ast.t
  let sexp_of_t = Ast.sexp_of_t String_with_vars.sexp_of_t String_with_vars.sexp_of_t

  let t sexp =
    match sexp with
    | Atom _ ->
      of_sexp_errorf sexp
        "if you meant for this to be executed with bash, write (bash \"...\") instead"
    | List _ -> Ast.t String_with_vars.t String_with_vars.t sexp

  let fold_vars t ~init ~f =
    Ast.fold t ~init ~f:(fun acc pat ->
      String_with_vars.fold ~init:acc pat ~f)

  let rec expand ctx dir t ~f : (string, Path.t) Ast.t =
    match t with
    | Run (prog, args) ->
      Run (expand_prog ctx ~dir ~f prog,
           List.map args ~f:(fun arg -> expand_str ~dir ~f arg))
    | Chdir (fn, t) ->
      let fn = expand_path ~dir ~f fn in
      Chdir (fn, expand ctx fn t ~f)
    | Setenv (var, value, t) ->
      Setenv (expand_str ~dir ~f var, expand_str ~dir ~f value,
              expand ctx dir t ~f)
    | Redirect (outputs, fn, t) ->
      Redirect (outputs, expand_path ~dir ~f fn, expand ctx dir t ~f)
    | Ignore (outputs, t) ->
      Ignore (outputs, expand ctx dir t ~f)
    | Progn l -> Progn (List.map l ~f:(fun t -> expand ctx dir t ~f))
    | Echo x -> Echo (expand_str ~dir ~f x)
    | Cat x -> Cat (expand_path ~dir ~f x)
    | Create_file x -> Create_file (expand_path ~dir ~f x)
    | Copy (x, y) ->
      Copy (expand_path ~dir ~f x, expand_path ~dir ~f y)
    | Symlink (x, y) ->
      Symlink (expand_path ~dir ~f x, expand_path ~dir ~f y)
    | Copy_and_add_line_directive (x, y) ->
      Copy_and_add_line_directive (expand_path ~dir ~f x, expand_path ~dir ~f y)
    | System x -> System (expand_str ~dir ~f x)
    | Bash x -> Bash (expand_str ~dir ~f x)
    | Update_file (x, y) -> Update_file (expand_path ~dir ~f x, expand_str ~dir ~f y)
    | Rename (x, y) ->
      Rename (expand_path ~dir ~f x, expand_path ~dir ~f y)
    | Remove_tree x ->
      Remove_tree (expand_path ~dir ~f x)
end

open Future

let get_std_output : _ -> Future.std_output_to = function
  | None          -> Terminal
  | Some (fn, oc) -> Opened_file { filename = fn; tail = false; desc = Channel oc }

let run ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to prog args =
  let stdout_to = get_std_output stdout_to in
  let stderr_to = get_std_output stderr_to in
  let env = Context.extend_env ~vars:env_extra ~env in
  Future.run Strict ~dir:(Path.to_string dir) ~env ~stdout_to ~stderr_to ~purpose
    (Path.reach_for_running ~from:dir prog) args

let rec exec t ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to =
  match t with
  | Run (prog, args) ->
    run ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to prog args
  | Chdir (dir, t) ->
    exec t ~purpose ~env ~env_extra ~stdout_to ~stderr_to ~dir
  | Setenv (var, value, t) ->
    exec t ~purpose ~dir ~env ~stdout_to ~stderr_to
      ~env_extra:(Env_var_map.add env_extra ~key:var ~data:value)
  | Redirect (outputs, fn, t) ->
    redirect ~purpose outputs fn t ~dir ~env ~env_extra ~stdout_to ~stderr_to
  | Ignore (outputs, t) ->
    redirect ~purpose outputs Config.dev_null t ~dir ~env ~env_extra ~stdout_to ~stderr_to
  | Progn l ->
    exec_list l ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to
  | Echo str ->
    return
      (match stdout_to with
       | None -> print_string str; flush stdout
       | Some (_, oc) -> output_string oc str)
  | Cat fn ->
    Io.with_file_in (Path.to_string fn) ~f:(fun ic ->
      let oc =
        match stdout_to with
        | None -> stdout
        | Some (_, oc) -> oc
      in
      Io.copy_channels ic oc);
    return ()
  | Create_file fn ->
    let fn = Path.to_string fn in
    if Sys.file_exists fn then Sys.remove fn;
    Unix.close (Unix.openfile fn [O_CREAT; O_TRUNC; O_WRONLY] 0o666);
    return ()
  | Copy (src, dst) ->
    Io.copy_file ~src:(Path.to_string src) ~dst:(Path.to_string dst);
    return ()
  | Symlink (src, dst) ->
    if Sys.win32 then
      Io.copy_file ~src:(Path.to_string src) ~dst:(Path.to_string dst)
    else begin
      let src =
        if Path.is_root dst then
          Path.to_string src
        else
          Path.reach ~from:(Path.parent dst) src
      in
      let dst = Path.to_string dst in
      match Unix.readlink dst with
      | target ->
        if target <> src then begin
          Unix.unlink dst;
          Unix.symlink src dst
        end
      | exception _ ->
        Unix.symlink src dst
    end;
    return ()
  | Copy_and_add_line_directive (src, dst) ->
    Io.with_file_in (Path.to_string src) ~f:(fun ic ->
      Io.with_file_out (Path.to_string dst) ~f:(fun oc ->
        let fn = Path.drop_build_context src in
        Printf.fprintf oc "# 1 %S\n" (Path.to_string fn);
        Io.copy_channels ic oc));
    return ()
  | System cmd ->
    let path, arg =
      Utils.system_shell_exn ~needed_to:"interpret (system ...) actions"
    in
    run ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to path [arg; cmd]
  | Bash cmd ->
    run ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to
      (Utils.bash_exn ~needed_to:"interpret (bash ...) actions")
      ["-e"; "-u"; "-o"; "pipefail"; "-c"; cmd]
  | Update_file (fn, s) ->
    let fn = Path.to_string fn in
    if Sys.file_exists fn && Io.read_file fn = s then
      ()
    else
      Io.write_file fn s;
    return ()
  | Rename (src, dst) ->
    Unix.rename (Path.to_string src) (Path.to_string dst);
    return ()
  | Remove_tree path ->
    Path.rm_rf path;
    return ()

and redirect outputs fn t ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to =
  let fn = Path.to_string fn in
  let oc = Io.open_out fn in
  let out = Some (fn, oc) in
  let stdout_to, stderr_to =
    match outputs with
    | Stdout -> (out, stderr_to)
    | Stderr -> (stdout_to, out)
    | Outputs -> (out, out)
  in
  exec t ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to >>| fun () ->
  close_out oc

and exec_list l ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to =
  match l with
  | [] ->
    Future.return ()
  | [t] ->
    exec t ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to
  | t :: rest ->
    exec t ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to >>= fun () ->
    exec_list rest ~purpose ~dir ~env ~env_extra ~stdout_to ~stderr_to

let exec ~targets ?context t =
  let env =
    match (context : Context.t option) with
    | None -> Lazy.force Context.initial_env
    | Some c -> c.env
  in
  let targets = Path.Set.elements targets in
  let purpose = Future.Build_job targets in
  exec t ~purpose ~dir:Path.root ~env ~env_extra:Env_var_map.empty
    ~stdout_to:None ~stderr_to:None

let sandbox t ~sandboxed ~deps ~targets =
  Ast.Progn
    [ Ast.Progn (List.filter_map deps ~f:(fun path ->
        if Path.is_local path then
          Some (Ast.Symlink (path, sandboxed path))
        else
          None))
    ; Ast.map t ~f1:(fun x -> x) ~f2:sandboxed
    ; Ast.Progn (List.filter_map targets ~f:(fun path ->
        if Path.is_local path then
          Some (Ast.Rename (sandboxed path, path))
        else
          None))
    ]