/*
   Copyright 2020 Kyle Gunger

   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 tparse

// Ops order in TNSL
// Cast/Paren > Address > Get > Inc/Dec > Math > Bitwise > Logic

var UNARY = map[string]int {
	"~": 0,
	"`": 0,
	"++": 2,
	"--": 2,
	"!": 6,

}

var ORDER = map[string]int{
	// Get
	".": 1,

	"is": 2,

	// Multiplication
	"*": 3,
	// Division
	"/": 3,

	// Addition
	"+": 4,
	// Subtraction
	"-": 4,
	
	// Mod
	"%": 5,

	// Bitwise and
	"&": 6,
	// Bitwise or
	"|": 6,
	// Bitwise xor
	"^": 6,

	// Bitwise l-shift
	"<<": 6,
	// Bitwise r-shift
	">>": 6,

	"!&": 6,
	"!|": 6,
	"!^": 6,

	// Boolean and
	"&&": 7,
	// Boolean or
	"||": 7,
	// Truthy equals
	"==": 7,

	// Greater than
	">": 7,
	// Less than
	"<": 7,

	"!&&": 7,
	"!||": 7,
	"!==": 7,

	"!>": 7,
	"!<": 7,

	// Assignement
	"=": 8,
}

// Works? Please test. 
func parseUnaryOps(tokens *[]Token, tok, max int) (Node) {
	out := Node{Data: Token{Type: 10, Data: "value"}, IsBlock: false}
	val := false

	// Pre-value op scan
	for ; tok < max && !val; tok++ {
		t := (*tokens)[tok]
		switch t.Type {
		case DELIMIT:
			var tmp Node
			switch t.Data {
			case "(": // Parenthetical value
				return parseBinaryOp(tokens, tok, max)
			case "{": // Array or struct evaluation
				tmp, _ = parseValueList(tokens, tok, max)
				return tmp
			default:
				errOut("Unexpected delimiter when parsing value", t)
			}
		case DEFWORD:
			fallthrough
		case LITERAL:
			out.Sub = append(out.Sub, Node{Data: t, IsBlock: false})
			val = true
		case AUGMENT:
			_, prs := UNARY[t.Data]
			if !prs {
				errOut("Parser bug!  Operator failed to load into AST.", t)
			} else {
				out.Sub = append(out.Sub, Node{Data: t, IsBlock: false})
			}
		default:
			errOut("Unexpected token in value declaration", t)
		}
	}

	// Sanity check: make sure there's actually a value here
	if !val {
		errOut("Expected to find value, but there wasn't one", (*tokens)[max])
	}

	// Post-value op scan
	for ; tok < max; tok++ {
		t := (*tokens)[tok]
		switch t.Type {
		case DELIMIT:
			var tmp Node
			switch t.Data {
			case "(": // Function call
				tmp, tok = parseValueList(tokens, tok, max)
				out.Sub = append(out.Sub, tmp)
			case "[": // Typecasting
				tmp, tok = parseType(tokens, tok, max, false)
				out.Sub = append(out.Sub, tmp)
			case "{": // Array indexing
				tmp = Node{Data: Token{Type: 10, Data: "index"}}
				var tmp2 Node
				tmp2, tok = parseValue(tokens, tok + 1, max)
				tmp.Sub = append(tmp.Sub, tmp2)
				out.Sub = append(out.Sub, tmp)
			default:
				errOut("Unexpected delimiter when parsing value", t)
			}
		case AUGMENT:
			_, prs := UNARY[t.Data]
			if !prs {
				errOut("Parser bug!  Operator failed to load into AST.", t)
			} else {
				out.Sub = append(out.Sub, Node{Data: t, IsBlock: false})
			}
		default:
			errOut("Unexpected token in value declaration", t)
		}
	}

	return out
}

//  Works?  Please test.
func parseBinaryOp(tokens *[]Token, tok, max int) (Node) {
	out := Node{IsBlock: false}
	first := tok
	var high, highOrder, bincount int = first, 8, 0
	var curl, brak, parn int = 0, 0, 0

	// Find first high-order op
	for ; tok < max; tok++ {
		t := (*tokens)[tok]
		if t.Type == DELIMIT {
			switch t.Data {
			case "{":
				curl++
			case "[":
				brak++
			case "(":
				parn++
			
			case "}":
				curl--
			case "]":
				brak--
			case ")":
				parn--
			}

			if curl < 0 || brak < 0 || parn < 0 {
				if curl > 0 || brak > 0 || parn > 0 {
					errOut("Un-matched closing delimiter when parsing a type.", t)
				}
			}
		} else if t.Type == AUGMENT {
			order, prs := ORDER[t.Data]
			if !prs || curl > 0 || brak > 0 || parn > 0 {
				continue
			} else if order > highOrder {
				high, highOrder = tok, order
			}
			// TODO: Add in case for the "is" operator
			bincount++
		}
	}

	out.Data = (*tokens)[high]

	if bincount == 0 {
		// No binops means we have a value to parse.  Parse all unary ops around it.
		return parseUnaryOps(tokens, first, max)
	} else {
		// Recursive split to lower order operations
		out.Sub = append(out.Sub, parseBinaryOp(tokens, first, high))
		out.Sub = append(out.Sub, parseBinaryOp(tokens, high + 1, max))
	}

	return out
}

// TODO: fix this
func parseValue(tokens *[]Token, tok, max int) (Node, int) {
	first := tok
	var curl, brak, parn int = 0, 0, 0

	for ; tok < max; tok++ {
		t := (*tokens)[tok]
		switch t.Type {
		case LINESEP:
			if curl > 0 || brak > 0 || parn > 0 {
				errOut("Encountered end of statement before all delimiter pairs were closed while looking for the end of a value.", t)
			}
			fallthrough
		case INLNSEP:
			if curl > 0 || brak > 0 || parn > 0 {
				continue
			}
			goto PARSEBIN
		case DELIMIT:
			switch t.Data {
			case "{":
				curl++
			case "[":
				brak++
			case "(":
				parn++
			
			case "}":
				curl--
			case "]":
				brak--
			case ")":
				parn--
			}

			if curl < 0 || brak < 0 || parn < 0 {
				if curl > 0 || brak > 0 || parn > 0 {
					errOut("Un-matched closing delimiter when parsing a value.", t)
				}
			}
		}
	}

	PARSEBIN:

	return parseBinaryOp(tokens, first, tok), tok
}

// TODO: make sure this actually works
func parseVoidType(tokens *[]Token, tok, max int) (Node, int) {
	out := Node{}
	working := &out

	for ; tok < max; tok++ {
		t := (*tokens)[tok]
		switch t.Type {
		case AUGMENT:
			if t.Data != "~" && t.Data != "`" {
				errOut("Error: unexpected augment token when parsing type", t)
			}
			working.Data = t

		case KEYTYPE:
			if t.Data == "void" {
				*working, tok = parseVoidType(tokens, tok, max)
			} else {
				working.Data = t
			}

			return out, tok

		case DEFWORD:

		case DELIMIT:
			if t.Data == "{" && tok < max-1 {
				if (*tokens)[tok+1].Data == "}" {
					working.Data = Token{AUGMENT, "{}", t.Line, t.Char}
					tok++
				} else {
					errOut("Error: start of list when parsing type (did you mean \"{}\"?)", t)
				}
			} else if tok >= max-1 {
				errOut("Error: unexpected end of file when parsing type", t)
			} else {
				errOut("Error: unexpected delimeter when parsing type", t)
			}

		default:
			errOut("Error: unexpected token when parsing type", t)
		}

		makeParent(working, Node{})
		working = &(working.Sub[0])
	}

	return out, tok
}

// TODO: make sure this actually works
func parseType(tokens *[]Token, tok, max int, param bool) (Node, int) {
	out := Node{Data: Token{Type: 10, Data: "type"}}
	working := &out

	for ; tok < max; tok++ {
		t := (*tokens)[tok]
		switch t.Type {
		case AUGMENT:
			if t.Data != "~" && t.Data != "`" {
				errOut("Error: unexpected augment token when parsing type", t)
			}
			working.Data = t

		case KEYTYPE:
			if t.Data == "void" {
				*working, tok = parseVoidType(tokens, tok, max)
			} else {
				working.Data = t
			}

			return out, tok

		case DEFWORD:
			if (*tokens)[tok+1].Data == "(" {

			}

		case KEYWORD:
			if param && t.Data == "static" {
				// Nonstandard keyword in parameter definition
				errOut("Error: parameter types cannot be static", t)
			} else if t.Data != "const" && t.Data != "volatile" && t.Data != "static" {
				// Nonstandard keyword in variable definition
				errOut("Error: unexpected keyword when parsing type", t)
			}
			working.Data = t

		case DELIMIT:
			if t.Data == "{" && tok < max-1 {
				// What happens when an array type is defined
				if (*tokens)[tok+1].Data == "}" {
					// Length variable array
					working.Data = Token{AUGMENT, "{}", t.Line, t.Char}
					tok++
				} else if (*tokens)[tok+1].Type == LITERAL {
					// Array with constant length
				} else {
					// Undefined behaviour
					errOut("Error: start of list when parsing type (did you mean \"{}\"?)", t)
				}
			} else if tok >= max-1 {
				// End of file with open delimiter after type parsing has begun
				errOut("Error: unexpected end of file when parsing type", t)
			} else {
				// Other delimiter than {} used in variable definition
				errOut("Error: unexpected delimeter when parsing type", t)
			}

		default:
			errOut("Error: unexpected token when parsing type", t)
		}

		makeParent(working, Node{})
		working = &(working.Sub[0])
	}

	return out, tok
}