package comp

import (
	"fmt"
	"reflect"
)

// Dump represents the state of a data dump.
type Dump struct {
	Values []*DumpValue
}

// DumpValue is a value of a dump state.
type DumpValue struct {
	Index int
	Name  string
	Kind  int
	Type  string
	Value any
}

// Dump creates a snapshot of the execution state of global variables.
// This method is specifically implemented in the Compiler to minimize the coupling between
// the dump format and other components. By situating the dump logic in the Compiler,
// it relies solely on the program being executed and the indexing algorithm used for ordering variables
// (currently, this is an integer that corresponds to the order of variables in the program).
// This design choice allows the Virtual Machine (VM) to evolve its memory management strategies
// without compromising backward compatibility with dumps generated by previous versions.
func (c *Compiler) Dump() *Dump {
	dict := c.symbolsByIndex()
	dv := make([]*DumpValue, len(c.Data))
	for i, d := range c.Data {
		e := dict[i]
		dv[i] = &DumpValue{
			Index: e.Index,
			Name:  e.name,
			Kind:  int(e.Kind),
			Type:  e.Type.Name,
			Value: d.Interface(),
		}
	}
	return &Dump{Values: dv}
}

// ApplyDump sets previously saved dump, restoring the state of global variables.
func (c *Compiler) ApplyDump(d *Dump) error {
	dict := c.symbolsByIndex()
	for _, dv := range d.Values {
		// do all the checks to be sure we are applying the correct values
		e, ok := dict[dv.Index]
		if !ok {
			return fmt.Errorf("entry not found on index %d", dv.Index)
		}

		if dv.Name != e.name ||
			dv.Type != e.Type.Name ||
			dv.Kind != int(e.Kind) {
			return fmt.Errorf("entry with index %d does not match with provided entry. "+
				"dumpValue: %s, %s, %d. memoryValue: %s, %s, %d",
				dv.Index,
				dv.Name, dv.Type, dv.Kind,
				e.name, e.Type, e.Kind)
		}

		if dv.Index >= len(c.Data) {
			return fmt.Errorf("index (%d) bigger than memory (%d)", dv.Index, len(c.Data))
		}

		if !c.Data[dv.Index].CanSet() {
			return fmt.Errorf("value %v cannot be set", dv.Value)
		}

		c.Data[dv.Index].Set(reflect.ValueOf(dv.Value))
	}
	return nil
}