package steering

import (
	"encoding/json"
	"fmt"
	"github.com/cyrilix/robocar-protobuf/go/events"
	"go.uber.org/zap"
	"os"
)

type Corrector struct {
	gridMap *GridMap
}

/*
AdjustFromObjectPosition modify steering value according object positions

 1. To compute steering correction, split in image in zones and define correction value for each zone

    Steering computed
    :  -1   -0.66 -0.33   0    0.33  0.66   1
    0%  |-----|-----|-----|-----|-----|-----|
    :   |  0  |  0  |  0  |  0  |  0  |  0  |
    20% |-----|-----|-----|-----|-----|-----|
    :   |  0  |  0  |  0  |  0  |  0  |  0  |
    40% |-----|-----|-----|-----|-----|-----|
    :   |  0  |  0  | 0.25|-0.25|  0  |  0  |
    60% |-----|-----|-----|-----|-----|-----|
    :   |  0  | 0.25| 0.5 |-0.5 |-0.25|  0  |
    80% |-----|-----|-----|-----|-----|-----|
    :   | 0.25| 0.5 |  1  |  -1 |-0.5 |-0.25|
    100%|-----|-----|-----|-----|-----|-----|

 2. For straight (current steering near of 0), search nearest object and if:

    * left and right values < 0: use correction from right value according image splitting
    * left and right values > 0: use correction from left value according image splitting
    * left < 0 and right values > 0: use (right + (right - left) / 2) value

 3. If current steering != 0 (turn on left or right), shift right and left values proportionnaly to current steering and
    apply 2.
*/
func (c *Corrector) AdjustFromObjectPosition(currentSteering float64, objects []*events.Object) float64 {
	// TODO, group rectangle

	if len(objects) == 0 {
		return currentSteering
	}
	// get nearest object
	nearest, err := c.nearObject(objects)
	if err != nil {
		zap.S().Warnf("unexpected error on nearest seach object, ignore objects: %v", err)
		return currentSteering
	}

	if currentSteering > 0.1 && currentSteering < 0.1 {

		if nearest.Bottom < 0.4 {
			// object is far, so no need to fix steering now
			return currentSteering
		}

		var delta float64

		if nearest.Left < 0 && nearest.Right < 0 {
			delta, err = c.gridMap.ValueOf(currentSteering, float64(nearest.Right))
		}
		if nearest.Left > 0 && nearest.Right > 0 {
			delta, err = c.gridMap.ValueOf(currentSteering, float64(nearest.Left))
		} else {
			delta, err = c.gridMap.ValueOf(currentSteering, float64(nearest.Left)+(float64(nearest.Right)-float64(nearest.Left))/2.)
		}
		if err != nil {
			zap.S().Warnf("unable to compute delta to apply to steering, skip correction: %v", err)
			delta = 0
		}
		return currentSteering + delta
	}

	// Search if current steering is near of Right or Left

	return currentSteering
}

func (c *Corrector) nearObject(objects []*events.Object) (*events.Object, error) {
	if len(objects) == 0 {
		return nil, fmt.Errorf("list objects must contain at least one object")
	}
	if len(objects) == 1 {
		return objects[0], nil
	}

	var result *events.Object
	for _, obj := range objects {
		if result == nil || obj.Bottom > result.Bottom {
			result = obj
			continue
		}
	}
	return result, nil
}

func NewGridMapFromJson(fileName string) (*GridMap, error) {
	content, err := os.ReadFile(fileName)
	if err != nil {
		return nil, fmt.Errorf("unable to read content from %s file: %w", fileName, err)
	}
	var ft GridMap
	err = json.Unmarshal(content, &ft)
	if err != nil {
		return nil, fmt.Errorf("unable to unmarshal json content from %s file: %w", fileName, err)
	}
	// TODO: check structure is valid
	return &ft, nil
}

type GridMap struct {
	DistanceSteps []float64   `json:"distance_steps"`
	SteeringSteps []float64   `json:"steering_steps"`
	Data          [][]float64 `json:"data"`
}

func (f *GridMap) ValueOf(steering float64, distance float64) (float64, error) {
	if steering < f.SteeringSteps[0] || steering > f.SteeringSteps[len(f.SteeringSteps)-1] {
		return 0., fmt.Errorf("invalid steering value: %v, must be between %v and %v", steering, f.SteeringSteps[0], f.SteeringSteps[len(f.SteeringSteps)-1])
	}
	if distance < f.DistanceSteps[0] || distance > f.DistanceSteps[len(f.DistanceSteps)-1] {
		return 0., fmt.Errorf("invalid distance value: %v, must be between %v and %v", steering, f.DistanceSteps[0], f.DistanceSteps[len(f.DistanceSteps)-1])
	}
	// search column index
	var idxCol int
	// Start loop at 1 because first column should be skipped
	for i := 1; i < len(f.SteeringSteps); i++ {
		if steering < f.SteeringSteps[i] {
			idxCol = i - 1
			break
		}
	}

	var idxRow int
	// Start loop at 1 because first column should be skipped
	for i := 1; i < len(f.DistanceSteps); i++ {
		if distance < f.DistanceSteps[i] {
			idxRow = i - 1
			break
		}
	}

	return f.Data[idxRow][idxCol], nil
}