------------------------------------------------------------------------
-- The Agda standard library
--
-- Finite maps with indexed keys and values, based on AVL trees
------------------------------------------------------------------------

{-# OPTIONS --without-K --safe #-}

open import Data.Product as Prod
open import Relation.Binary
open import Relation.Binary.PropositionalEquality using (_≡_; cong; subst)
import Data.Tree.AVL.Value

module Data.Tree.AVL.IndexedMap
  {i k v ℓ}
  {Index : Set i} {Key : Index → Set k}  (Value : Index → Set v)
  {_<_ : Rel (∃ Key) ℓ}
  (isStrictTotalOrder : IsStrictTotalOrder _≡_ _<_)
  where

import Data.Tree.AVL
open import Data.Bool.Base using (Bool)
open import Data.List.Base as List using (List)
open import Data.Maybe.Base as Maybe using (Maybe)
open import Data.Nat.Base using (ℕ)
open import Function.Base
open import Level using (Level; _⊔_)

private
  variable
    a : Level
    A : Set a

-- Key/value pairs.

KV : Set (i ⊔ k ⊔ v)
KV = ∃ λ i → Key i × Value i

-- Conversions.

private

  fromKV : KV → Σ[ ik ∈ ∃ Key ] Value (proj₁ ik)
  fromKV (i , k , v) = ((i , k) , v)

  toKV : Σ[ ik ∈ ∃ Key ] Value (proj₁ ik) → KV
  toKV ((i , k) , v) = (i , k , v)

-- The map type.

private
  open module AVL =
    Data.Tree.AVL (record { isStrictTotalOrder = isStrictTotalOrder })
    using () renaming (Tree to Map′)
  Map = Map′ (AVL.MkValue (Value ∘ proj₁) (subst Value ∘′ cong proj₁))

-- Repackaged functions.

empty : Map
empty = AVL.empty

singleton : ∀ {i} → Key i → Value i → Map
singleton k v = AVL.singleton (-, k) v

insert : ∀ {i} → Key i → Value i → Map → Map
insert k v = AVL.insert (-, k) v

delete : ∀ {i} → Key i → Map → Map
delete k = AVL.delete (-, k)

lookup : ∀ {i} → Key i → Map → Maybe (Value i)
lookup k m = AVL.lookup (-, k) m

infix  _∈?_

_∈?_ : ∀ {i} → Key i → Map → Bool
_∈?_ k = AVL._∈?_ (-, k)

headTail : Map → Maybe (KV × Map)
headTail m = Maybe.map (Prod.map toKV id) (AVL.headTail m)

initLast : Map → Maybe (Map × KV)
initLast m = Maybe.map (Prod.map id toKV) (AVL.initLast m)

foldr : (∀ {k} → Value k → A → A) → A → Map → A
foldr cons = AVL.foldr cons

fromList : List KV → Map
fromList = AVL.fromList ∘ List.map fromKV

toList : Map → List KV
toList = List.map toKV ∘ AVL.toList

size : Map → ℕ
size = AVL.size