// Copyright 2020 The Ebiten Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Package shaderir offers intermediate representation for shader programs.
package shaderir

type Program struct {
	Uniforms     []Type
	Attributes   []Type
	Varyings     []Type
	Funcs        []Func
	VertexFunc   VertexFunc
	FragmentFunc FragmentFunc

	structNames map[string]string
	structTypes []Type
}

// TODO: How to avoid the name with existing functions?

type Func struct {
	Name        string
	InParams    []Type
	InOutParams []Type
	OutParams   []Type
	Return      Type
	Block       Block
}

// VertexFunc takes pseudo params, and the number if len(attributes) + len(varyings) + 1.
// If 0 <= index < len(attributes), the params are in-params and treated as attribute variables.
// If len(attributes) <= index < len(attributes) + len(varyings), the params are out-params and treated as varying
// variables.
// The last param represents the position in vec4 (gl_Position in GLSL).
type VertexFunc struct {
	Block Block
}

// FragmentFunc takes pseudo in-params, and the number is len(varyings) + 1.
// The last param represents the coordinate of the fragment (gl_FragCoord in GLSL)
type FragmentFunc struct {
	Block Block
}

type Block struct {
	LocalVars []Type
	Stmts     []Stmt
}

type Stmt struct {
	Type     StmtType
	Exprs    []Expr
	Blocks   []Block
	ForInit  int
	ForEnd   int
	ForOp    Op
	ForDelta int
}

type StmtType int

const (
	ExprStmt StmtType = iota
	BlockStmt
	Assign
	If
	For
	Continue
	Break
	Return
	Discard
)

type Expr struct {
	Type        ExprType
	Exprs       []Expr
	Variable    Variable
	Int         int32
	Float       float32
	BuiltinFunc BuiltinFunc
	Ident       string
	Op          Op
}

type ExprType int

const (
	IntExpr ExprType = iota
	FloatExpr
	VarName
	BuiltinFuncExpr
	Ident
	Unary
	Binary
	Selection
	Call
	FieldSelector
	Index
)

type Variable struct {
	Type  VariableType
	Index int
}

type VariableType int

const (
	Uniform VariableType = iota
	Local
)

type Op string

const (
	Add                Op = "+"
	Sub                Op = "-"
	Neg                Op = "!"
	Mul                Op = "*"
	Div                Op = "/"
	ModOp              Op = "%"
	LeftShift          Op = "<<"
	RightShift         Op = ">>"
	LessThanOp         Op = "<"
	LessThanEqualOp    Op = "<="
	GreaterThanOp      Op = ">"
	GreaterThanEqualOp Op = ">="
	EqualOp            Op = "=="
	NotEqualOp         Op = "!="
	And                Op = "&"
	Xor                Op = "^"
	Or                 Op = "|"
	AndAnd             Op = "&&"
	OrOr               Op = "||"
)

type BuiltinFunc string

const (
	Radians          BuiltinFunc = "radians"
	Degrees          BuiltinFunc = "degrees"
	Sin              BuiltinFunc = "sin"
	Cos              BuiltinFunc = "cos"
	Tan              BuiltinFunc = "tan"
	Asin             BuiltinFunc = "asin"
	Acos             BuiltinFunc = "acos"
	Atan             BuiltinFunc = "atan"
	Pow              BuiltinFunc = "pow"
	Exp              BuiltinFunc = "exp"
	Log              BuiltinFunc = "log"
	Exp2             BuiltinFunc = "exp2"
	Log2             BuiltinFunc = "log2"
	Sqrt             BuiltinFunc = "sqrt"
	Inversesqrt      BuiltinFunc = "inversesqrt"
	Abs              BuiltinFunc = "abs"
	Sign             BuiltinFunc = "sign"
	Floor            BuiltinFunc = "floor"
	Ceil             BuiltinFunc = "ceil"
	Fract            BuiltinFunc = "fract"
	Mod              BuiltinFunc = "mod"
	Min              BuiltinFunc = "min"
	Max              BuiltinFunc = "max"
	Clamp            BuiltinFunc = "clamp"
	Mix              BuiltinFunc = "mix"
	Step             BuiltinFunc = "step"
	Smoothstep       BuiltinFunc = "smoothstep"
	Length           BuiltinFunc = "length"
	Distance         BuiltinFunc = "distance"
	Dot              BuiltinFunc = "dot"
	Cross            BuiltinFunc = "cross"
	Normalize        BuiltinFunc = "normalize"
	Faceforward      BuiltinFunc = "faceforward"
	Reflect          BuiltinFunc = "reflect"
	MatrixCompMult   BuiltinFunc = "matrixCompMult"
	OuterProduct     BuiltinFunc = "outerProduct"
	Transpose        BuiltinFunc = "transpose"
	LessThan         BuiltinFunc = "lessThan"
	LessThanEqual    BuiltinFunc = "lessThanEqual"
	GreaterThan      BuiltinFunc = "greaterThan"
	GreaterThanEqual BuiltinFunc = "greaterThanEqual"
	Equal            BuiltinFunc = "equal"
	NotEqual         BuiltinFunc = "notEqual"
	Any              BuiltinFunc = "any"
	All              BuiltinFunc = "all"
	Not              BuiltinFunc = "not"
	Texture2D        BuiltinFunc = "texture2D"
)