package grow

import "io"

import "gopkg.in/yaml.v2"

import "github.com/firestuff/subcoding/vm"

type Definition struct {
	GlobalMemorySize   uint64    `yaml:"global_memory_size"`
	FunctionMemorySize uint64    `yaml:"function_memory_size"`
	InstructionLimit   uint64    `yaml:"instruction_limit"`
	Samples            []*Sample `yaml:"samples"`
}

func NewDefinition(r io.Reader) (*Definition, error) {
	dec := yaml.NewDecoder(r)
	dec.SetStrict(true)

	def := &Definition{}

	err := dec.Decode(def)
	if err != nil {
		return nil, err
	}

	return def, nil
}

func (def *Definition) Grow(statusChan chan<- Status) (*vm.Program, error) {
	status := Status{
		TargetScore: def.sumOuts(),
	}

	if statusChan != nil {
		statusChan <- status
	}

	prog := &vm.Program{
		GlobalMemorySize:   def.GlobalMemorySize,
		FunctionMemorySize: def.FunctionMemorySize,
		InstructionLimit:   def.InstructionLimit,
		Functions: []*vm.Function{
			&vm.Function{},
		},
	}

	for {
		status.Attempts++

		Mutate(prog)

		score, err := def.score(prog)
		if err != nil {
			// Can never get best score
			continue
		}

		if score > status.BestScore {
			status.BestScore = score
			status.BestProgram = prog

			if statusChan != nil {
				statusChan <- status
			}

			if status.BestScore == status.TargetScore {
				err = def.minifyProgram(prog)
				if err != nil {
					if statusChan != nil {
						close(statusChan)
					}

					return nil, err
				}

				if statusChan != nil {
					statusChan <- status
				}

				if statusChan != nil {
					close(statusChan)
				}

				return prog, nil
			}
		}
	}
}

func (def *Definition) score(prog *vm.Program) (uint64, error) {
	score := uint64(0)

	for _, sample := range def.Samples {
		state, err := vm.NewState(prog)
		if err != nil {
			return 0, err
		}

		sample.SetInputs(state)

		err = state.Execute()
		if err != nil {
			return 0, err
		}

		score += sample.matchingOuts(state)
	}

	return score, nil
}

func (def *Definition) sumOuts() uint64 {
	sum := uint64(0)

	for _, sample := range def.Samples {
		sum += uint64(len(sample.Out))
	}

	return sum
}

func (def *Definition) minifyProgram(prog *vm.Program) error {
	for f := 0; f < len(prog.Functions); f++ {
		err := def.minifyFunction(prog, f)
		if err != nil {
			return err
		}
	}

	return nil
}

func (def *Definition) minifyFunction(prog *vm.Program, f int) error {
	baseScore, err := def.score(prog)
	if err != nil {
		return err
	}

	for loop := true; loop; {
		loop = false

		for i := 0; i < len(prog.Functions[f].Instructions); i++ {
			origInstructions := prog.Functions[f].Instructions
			tmp := make([]*vm.Instruction, len(prog.Functions[f].Instructions))
			copy(tmp, prog.Functions[f].Instructions)
			prog.Functions[f].Instructions = append(tmp[:i], tmp[i+1:]...)

			newScore, err := def.score(prog)
			if err == nil && newScore >= baseScore {
				loop = true
				break
			} else {
				prog.Functions[f].Instructions = origInstructions
			}
		}
	}

	return nil
}