package compiler

import (
	"fmt"
	"go/ast"
	"go/types"
)

// A funcScope represents the scope within the function context.
// It holds all the local variables along with the initialized struct positions.
type funcScope struct {
	// Identifier of the function.
	name string

	// Selector of the function if there is any. Only functions imported
	// from other packages should have a selector.
	selector ast.Expr

	// The declaration of the function in the AST. Nil if this scope is not a function.
	decl *ast.FuncDecl

	// Package where the function is defined.
	pkg *types.Package

	file *ast.File

	// Program label of the scope
	label uint16

	// Range of opcodes corresponding to the function.
	rng DebugRange
	// Variables together with it's type in neo-vm.
	variables []string

	// deferStack is a stack containing encountered `defer` statements.
	deferStack []deferInfo

	// Local variables
	vars varScope

	// voidCalls are basically functions that return their value
	// into nothing. The stack has their return value but there
	// is nothing that consumes it. We need to keep track of
	// these functions so we can cleanup (drop) the returned
	// value from the stack. We also need to add every voidCall
	// return value to the stack size.
	voidCalls map[*ast.CallExpr]bool

	// Local variable counter.
	i int
}

type deferInfo struct {
	catchLabel   uint16
	finallyLabel uint16
	expr         *ast.CallExpr
	localIndex   int
}

const (
	finallyVarName   = "<finally>"
	exceptionVarName = "<exception>"
)

func (c *codegen) newFuncScope(decl *ast.FuncDecl, label uint16) *funcScope {
	var name string
	if decl.Name != nil {
		name = decl.Name.Name
	}
	return &funcScope{
		name:      name,
		decl:      decl,
		label:     label,
		pkg:       c.currPkg.Types,
		vars:      newVarScope(),
		voidCalls: map[*ast.CallExpr]bool{},
		variables: []string{},
		i:         -1,
	}
}

func (c *codegen) getFuncNameFromDecl(pkgPath string, decl *ast.FuncDecl) string {
	name := decl.Name.Name
	if decl.Recv != nil {
		switch t := decl.Recv.List[0].Type.(type) {
		case *ast.Ident:
			name = t.Name + "." + name
		case *ast.StarExpr:
			switch t.X.(type) {
			case *ast.Ident:
				name = t.X.(*ast.Ident).Name + "." + name
			case *ast.IndexExpr:
				// Generic func declaration receiver: func (x *Pointer[T]) Load() *T
				name = t.X.(*ast.IndexExpr).X.(*ast.Ident).Name + "." + name
			default:
				panic(fmt.Errorf("unexpected function `%s` receiver type: %T", name, t.X))
			}
		case *ast.IndexExpr:
			switch t.X.(type) {
			case *ast.Ident:
				// Generic func declaration receiver: func (x Pointer[T]) Load() *T
				name = t.X.(*ast.Ident).Name + "." + name
			default:
				panic(fmt.Errorf("unexpected function `%s` receiver type: %T", name, t.X))
			}
		}
	}
	return c.getIdentName(pkgPath, name)
}

// analyzeVoidCalls checks for functions that are not assigned
// and therefore we need to cleanup the return value from the stack.
func (c *funcScope) analyzeVoidCalls(node ast.Node) bool {
	est, ok := node.(*ast.ExprStmt)
	if ok {
		ce, ok := est.X.(*ast.CallExpr)
		if ok {
			c.voidCalls[ce] = true
		}
	}
	return true
}

func (c *funcScope) countArgs() int {
	n := c.decl.Type.Params.NumFields()
	if c.decl.Recv != nil {
		n += c.decl.Recv.NumFields()
	}
	return n
}

// newVariable creates a new local variable or argument in the scope of the function.
func (c *funcScope) newVariable(t varType, name string) int {
	return c.vars.newVariable(t, name)
}

// newLocal creates a new local variable into the scope of the function.
func (c *funcScope) newLocal(name string) int {
	return c.newVariable(varLocal, name)
}