#+private file

package server

import "core:fmt"
import "core:log"
import "core:odin/ast"
import "core:odin/tokenizer"
import path "core:path/slashpath"
import "core:strings"

import "src:common"

/*
 * The general idea behind inverting if statements is to allow 
 * if statements to be inverted without changing their behavior.
 * The examples of these changes are provided in the tests.
 * We should be careful to only allow this code action when it is safe to do so.
 * So for now, we only support only one level of if statements without else-if chains.
 */

@(private="package")
add_invert_if_action :: proc(
	document: ^Document,
	position: common.AbsolutePosition,
	uri: string,
	actions: ^[dynamic]CodeAction,
) {
	if_stmt := find_if_stmt_at_position(document.ast.decls[:], position)
	if if_stmt == nil {
		return
	}

	new_text, ok := generate_inverted_if(document, if_stmt)
	if !ok {
		return
	}

	range := common.get_token_range(if_stmt^, document.ast.src)

	textEdits := make([dynamic]TextEdit, context.temp_allocator)
	append(&textEdits, TextEdit{range = range, newText = new_text})

	workspaceEdit: WorkspaceEdit
	workspaceEdit.changes = make(map[string][]TextEdit, 0, context.temp_allocator)
	workspaceEdit.changes[uri] = textEdits[:]

	append(
		actions,
		CodeAction {
			kind = "refactor.more",
			isPreferred = false,
			title = "Invert if",
			edit = workspaceEdit,
		},
	)
}

// Find the innermost if statement that contains the given position
// This will NOT return else-if statements, only top-level if statements
// Also will not return an if statement if the position is in its else clause
find_if_stmt_at_position :: proc(stmts: []^ast.Stmt, position: common.AbsolutePosition) -> ^ast.If_Stmt {
	for stmt in stmts {
		if stmt == nil {
			continue
		}
		if result := find_if_stmt_in_node(stmt, position, false); result != nil {
			return result
		}
	}
	return nil
}

find_if_stmt_in_node :: proc(node: ^ast.Node, position: common.AbsolutePosition, in_else_clause: bool) -> ^ast.If_Stmt {
	if node == nil {
		return nil
	}

	if !(node.pos.offset <= position && position <= node.end.offset) {
		return nil
	}

	#partial switch n in node.derived {
	case ^ast.If_Stmt:
		// First check if position is in the else clause
		if n.else_stmt != nil && position_in_node(n.else_stmt, position) {
			// Position is in the else clause - look for nested ifs inside it
			// but mark that we're in an else clause
			if nested := find_if_stmt_in_node(n.else_stmt, position, true); nested != nil {
				return nested
			}
			// Position is in else clause but not on a valid nested if
			// Don't return the current if statement
			return nil
		}

		if n.body != nil && position_in_node(n.body, position) {
			if nested := find_if_stmt_in_node(n.body, position, false); nested != nil {
				return nested
			}
			// Position is inside the body but no nested if found
			// Don't return the current if statement
			return nil
		}

		// Position is in the condition/init part or we're the closest if
		// Only return this if statement if we're NOT in an else clause
		// (i.e., this is not an else-if)
		if !in_else_clause {
			return n
		}
		return nil

	case ^ast.Block_Stmt:
		for stmt in n.stmts {
			if result := find_if_stmt_in_node(stmt, position, false); result != nil {
				return result
			}
		}

	case ^ast.Proc_Lit:
		if n.body != nil {
			return find_if_stmt_in_node(n.body, position, false)
		}

	case ^ast.Value_Decl:
		for value in n.values {
			if result := find_if_stmt_in_node(value, position, false); result != nil {
				return result
			}
		}

	case ^ast.For_Stmt:
		if n.body != nil {
			return find_if_stmt_in_node(n.body, position, false)
		}

	case ^ast.Range_Stmt:
		if n.body != nil {
			return find_if_stmt_in_node(n.body, position, false)
		}

	case ^ast.Switch_Stmt:
		if n.body != nil {
			return find_if_stmt_in_node(n.body, position, false)
		}

	case ^ast.Type_Switch_Stmt:
		if n.body != nil {
			return find_if_stmt_in_node(n.body, position, false)
		}

	case ^ast.Case_Clause:
		for stmt in n.body {
			if result := find_if_stmt_in_node(stmt, position, false); result != nil {
				return result
			}
		}

	case ^ast.When_Stmt:
		if n.body != nil {
			if result := find_if_stmt_in_node(n.body, position, false); result != nil {
				return result
			}
		}
		if n.else_stmt != nil {
			if result := find_if_stmt_in_node(n.else_stmt, position, false); result != nil {
				return result
			}
		}

	case ^ast.Defer_Stmt:
		if n.stmt != nil {
			return find_if_stmt_in_node(n.stmt, position, false)
		}
	}

	return nil
}

// Generate the inverted if statement text
generate_inverted_if :: proc(document: ^Document, if_stmt: ^ast.If_Stmt) -> (string, bool) {
	src := document.ast.src

	indent := get_line_indentation(src, if_stmt.pos.offset)

	sb := strings.builder_make(context.temp_allocator)

	if if_stmt.label != nil {
		label_text := src[if_stmt.label.pos.offset:if_stmt.label.end.offset]
		strings.write_string(&sb, label_text)
		strings.write_string(&sb, ": ")
	}

	strings.write_string(&sb, "if ")

	if if_stmt.init != nil {
		init_text := src[if_stmt.init.pos.offset:if_stmt.init.end.offset]
		strings.write_string(&sb, init_text)
		strings.write_string(&sb, "; ")
	}

	if if_stmt.cond != nil {
		inverted_cond, ok := invert_condition(src, if_stmt.cond)
		if !ok {
			return "", false
		}
		strings.write_string(&sb, inverted_cond)
	}

	strings.write_string(&sb, " ")

	// Now we need to swap the bodies

	if if_stmt.else_stmt != nil {
		else_body_text := get_block_body_text(src, if_stmt.else_stmt, indent)
		then_body_text := get_block_body_text(src, if_stmt.body, indent)

		strings.write_string(&sb, "{\n")
		strings.write_string(&sb, else_body_text)
		strings.write_string(&sb, indent)
		strings.write_string(&sb, "} else {\n")
		strings.write_string(&sb, then_body_text)
		strings.write_string(&sb, indent)
		strings.write_string(&sb, "}")
	} else {
		then_body_text := get_block_body_text(src, if_stmt.body, indent)

		strings.write_string(&sb, "{\n")
		strings.write_string(&sb, indent)
		strings.write_string(&sb, "} else {\n")
		strings.write_string(&sb, then_body_text)
		strings.write_string(&sb, indent)
		strings.write_string(&sb, "}")
	}

	return strings.to_string(sb), true
}

// Get the indentation (leading whitespace) of the line containing the given offset
@(private="package")
get_line_indentation :: proc(src: string, offset: int) -> string {
	line_start := offset
	for line_start > 0 && src[line_start - 1] != '\n' {
		line_start -= 1
	}

	indent_end := line_start
	for indent_end < len(src) && (src[indent_end] == ' ' || src[indent_end] == '\t') {
		indent_end += 1
	}

	return src[line_start:indent_end]
}

// Extract the body text from a block statement (without the braces)
get_block_body_text :: proc(src: string, stmt: ^ast.Stmt, base_indent: string) -> string {
	if stmt == nil {
		return ""
	}

	#partial switch block in stmt.derived {
	case ^ast.Block_Stmt:
		if len(block.stmts) == 0 {
			return ""
		}

		sb := strings.builder_make(context.temp_allocator)

		for s in block.stmts {
			if s == nil {
				continue
			}
			stmt_indent := get_line_indentation(src, s.pos.offset)
			stmt_text := src[s.pos.offset:s.end.offset]
			strings.write_string(&sb, stmt_indent)
			strings.write_string(&sb, stmt_text)
			strings.write_string(&sb, "\n")
		}

		return strings.to_string(sb)

	case ^ast.If_Stmt:
		// This is an else-if, need to handle it recursively
		if_text, ok := generate_inverted_if_for_else(src, block, base_indent)
		if ok {
			return if_text
		}
	}

	// Fallback: just return the statement text
	stmt_text := src[stmt.pos.offset:stmt.end.offset]
	return fmt.tprintf("%s%s\n", base_indent, stmt_text)
}

// For else-if chains, we don't invert them, just preserve
generate_inverted_if_for_else :: proc(src: string, if_stmt: ^ast.If_Stmt, base_indent: string) -> (string, bool) {
	stmt_indent := get_line_indentation(src, if_stmt.pos.offset)
	stmt_text := src[if_stmt.pos.offset:if_stmt.end.offset]
	return fmt.tprintf("%s%s\n", stmt_indent, stmt_text), true
}

// Invert a condition expression
invert_condition :: proc(src: string, cond: ^ast.Expr) -> (string, bool) {
	if cond == nil {
		return "", false
	}

	#partial switch c in cond.derived {
	case ^ast.Binary_Expr:
		inverted_op, can_invert := get_inverted_operator(c.op.kind)
		if can_invert {
			left_text := src[c.left.pos.offset:c.left.end.offset]
			right_text := src[c.right.pos.offset:c.right.end.offset]
			return fmt.tprintf("%s %s %s", left_text, inverted_op, right_text), true
		}

		if c.op.kind == .Cmp_And || c.op.kind == .Cmp_Or {
			// Just wrap with !()
			cond_text := src[cond.pos.offset:cond.end.offset]
			return fmt.tprintf("!(%s)", cond_text), true
		}

	case ^ast.Unary_Expr:
		// If it's already negated with !, remove the negation
		if c.op.kind == .Not {
			inner_text := src[c.expr.pos.offset:c.expr.end.offset]
			return inner_text, true
		}

	case ^ast.Paren_Expr:
		inner_inverted, ok := invert_condition(src, c.expr)
		if ok {
			if needs_parentheses(inner_inverted) {
				return fmt.tprintf("(%s)", inner_inverted), true
			}
			return inner_inverted, true
		}
	}

	// Default: wrap the whole condition with !()
	cond_text := src[cond.pos.offset:cond.end.offset]
	if is_simple_expr(cond) {
		return fmt.tprintf("!%s", cond_text), true
	}
	return fmt.tprintf("!(%s)", cond_text), true
}

// Check if an expression is simple (identifier, call, or already parenthesized)
is_simple_expr :: proc(expr: ^ast.Expr) -> bool {
	if expr == nil {
		return false
	}
	#partial switch e in expr.derived {
	case ^ast.Ident, ^ast.Paren_Expr, ^ast.Call_Expr, ^ast.Selector_Expr, ^ast.Index_Expr:
		return true
	}
	return false
}

// Check if a string needs parentheses (simple heuristic)
needs_parentheses :: proc(s: string) -> bool {
	// If it starts with ! and is not wrapped in parens, it might need them
	// This is a simple heuristic
	return strings.contains(s, " && ") || strings.contains(s, " || ")
}

// Get the inverted comparison operator
get_inverted_operator :: proc(op: tokenizer.Token_Kind) -> (string, bool) {
	#partial switch op {
	case .Cmp_Eq:
		return "!=", true
	case .Not_Eq:
		return "==", true
	case .Lt:
		return ">=", true
	case .Lt_Eq:
		return ">", true
	case .Gt:
		return "<=", true
	case .Gt_Eq:
		return "<", true
	}
	return "", false
}