package template

import (
	"errors"
	"fmt"
	"maps"
	"math"
	"strconv"

	"git.wtrh.nl/patterns/gopatterns/pkg/pattern"
	"git.wtrh.nl/patterns/gopatterns/pkg/pattern/point"
	"gopkg.in/Knetic/govaluate.v3"
)

const maxRecursionDepth = 100

var (
	// ErrPointNotFound is returned when a required point is not defined.
	ErrPointNotFound = errors.New("required point not found")

	// ErrRelativePointRecursion is returned when a points are relative to itself.
	ErrRelativePointRecursion = errors.New("point cannot be relative to itself")

	ErrInvalidArguments = errors.New("invalid arguments to call function")
)

// Points contains a map with points.
type Points map[point.ID]Point

// Point contains the template information for a point.
type Point struct {
	Position    Position      `yaml:"position"`
	RelativeTo  *point.ID     `yaml:"relativeTo,omitempty"`
	Description string        `yaml:"description"`
	Between     *BetweenPoint `yaml:"between"`
	Extend      *ExtendPoint  `yaml:"extend"`
	Hide        bool          `yaml:"hide"`
	Polar       *PolarPoint   `yaml:"polar"`
}

var ErrInvalidPointID = errors.New("type cannot be converted to a PointID")

func (p Points) Functions(pat *pattern.Pattern) map[string]govaluate.ExpressionFunction {
	functions := p.evaluationFunctions()

	maps.Copy(functions, map[string]govaluate.ExpressionFunction{
		"DistanceBetween": func(args ...interface{}) (interface{}, error) {
			if len(args) != 2 {
				return nil, fmt.Errorf("function DistanceBetween() requires 2 arguments: %w",
					ErrInvalidArguments)
			}

			points, err := p.getOrCreateFromArgs(pat, args...)
			if err != nil {
				return nil, err
			}
			return points[0].Position().Distance(points[1].Position()), nil
		},
		"AngleBetween": func(args ...interface{}) (interface{}, error) {
			if len(args) != 2 {
				return nil, fmt.Errorf("function AngleBetween() requires 2 arguments: %w",
					ErrInvalidArguments)
			}

			points, err := p.getOrCreateFromArgs(pat, args...)
			if err != nil {
				return nil, err
			}

			return points[0].Vector().AngleBetween(points[1].Vector()), nil
		},
		"YDistanceBetween": func(args ...interface{}) (interface{}, error) {
			if len(args) != 2 {
				return nil, fmt.Errorf("function DistanceBetween() requires 2 arguments: %w",
					ErrInvalidArguments)
			}

			points, err := p.getOrCreateFromArgs(pat, args...)
			if err != nil {
				return nil, err
			}

			return points[0].Vector().Y - points[1].Vector().Y, nil
		},
		"XDistanceBetween": func(args ...interface{}) (interface{}, error) {
			if len(args) != 2 {
				return nil, fmt.Errorf("function DistanceBetween() requires 2 arguments: %w",
					ErrInvalidArguments)
			}

			points, err := p.getOrCreateFromArgs(pat, args...)
			if err != nil {
				return nil, err
			}

			return points[0].Vector().X - points[1].Vector().X, nil
		},
	})

	return functions
}

func (p Points) getOrCreateFromArgs(pat *pattern.Pattern, args ...interface{}) ([]point.Point, error) {
	points := make([]point.Point, 0, len(args))

	for i, arg := range args {
		id, err := toPointID(arg)
		if err != nil {
			return nil, fmt.Errorf("parsing args[%d] to pointID: %w", i, err)
		}

		newPoint, err := p.getOrCreate(id, pat, 0)
		if err != nil {
			return nil, fmt.Errorf("get or create point %q: %w", id, err)
		}

		points = append(points, newPoint)
	}

	return points, nil
}

func toPointID(arg interface{}) (point.ID, error) {
	v1, ok := arg.(string)
	if !ok {
		f, ok := arg.(float64)
		if !ok {
			return "", fmt.Errorf("parsing %v as PointID: %w", arg, ErrInvalidPointID)
		}

		v1 = strconv.FormatFloat(f, 'f', -1, 64)
	}

	id1 := point.ID(v1)

	return id1, nil
}

// BetweenPoint contains the template information for a point in between two other points.
type BetweenPoint struct {
	From   point.ID `yaml:"from"`
	To     point.ID `yaml:"to"`
	Offset *Value   `yaml:"offset"`
}

func (p Points) evaluationFunctions() map[string]govaluate.ExpressionFunction {
	return map[string]govaluate.ExpressionFunction{
		"acos": func(args ...interface{}) (interface{}, error) {
			if len(args) != 1 {
				return nil, fmt.Errorf("function acos() requires 1 argument: %w",
					ErrInvalidArguments)
			}

			x, ok := args[0].(float64)
			if !ok {
				return nil, fmt.Errorf("evaluate acos(): parsing %q as float64: %w", args[0],
					ErrInvalidArguments)
			}

			return math.Acos(x), nil
		},
		"asin": func(args ...interface{}) (interface{}, error) {
			if len(args) != 1 {
				return nil, fmt.Errorf("function asin() requires 1 argument: %w",
					ErrInvalidArguments)
			}

			x, ok := args[0].(float64)
			if !ok {
				return nil, fmt.Errorf("evaluate asin(): parsing %q as float64: %w", args[0],
					ErrInvalidArguments)
			}

			return math.Asin(x), nil
		},
		"atan2": func(args ...interface{}) (interface{}, error) {
			if len(args) != 2 {
				return nil, fmt.Errorf("function atan2() requires 2 arguments: %w",
					ErrInvalidArguments)
			}
			x, ok := args[0].(float64)
			if !ok {
				return nil, fmt.Errorf("evaluate atan2(): parsing %q as float64: %w", args[0],
					ErrInvalidArguments)
			}

			y, ok := args[1].(float64)
			if !ok {
				return nil, fmt.Errorf("evaluate atan2(): parsing %q as float64: %w", args[0],
					ErrInvalidArguments)
			}

			return math.Atan2(x, y), nil
		},
	}
}

// AddToPattern will add all points to the provided [pattern.Pattern].
func (p Points) AddToPattern(pat *pattern.Pattern) error {
	for id := range p {
		if pat.GetPoint(id) == nil {
			err := p.addSingleToPattern(id, pat, 0)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

func (p Points) addSingleToPattern(id point.ID, pat *pattern.Pattern, depth int) (err error) {
	templatePoint, ok := p[id]
	if !ok {
		return ErrPointNotFound
	}

	var newPoint point.Point

	switch {
	case templatePoint.RelativeTo != nil && templatePoint.Polar != nil:
		newPoint, err = p.createPolar(id, pat, depth)
		if err != nil {
			return err
		}
	case templatePoint.RelativeTo != nil:
		newPoint, err = p.createRelative(id, pat, depth)
		if err != nil {
			return err
		}
	case templatePoint.Between != nil:
		newPoint, err = p.createBetween(id, pat, depth)
		if err != nil {
			return err
		}
	case templatePoint.Extend != nil:
		newPoint, err = p.createExtend(id, pat, depth)
		if err != nil {
			return err
		}
	default:
		x, y, r, err := templatePoint.Position.evaluate(pat.Parameters(), p.Functions(pat))
		if err != nil {
			return err
		}

		newPoint = point.NewAbsolutePoint(x, y, r, id)
	}

	if templatePoint.Hide {
		newPoint.SetHide()
	}

	pat.AddPoint(newPoint)

	return nil
}

func (p Points) createRelative(
	id point.ID,
	pat *pattern.Pattern,
	depth int,
) (*point.RelativePoint, error) {
	templatePoint, ok := p[id]
	if !ok {
		return nil, ErrPointNotFound
	}

	relativePointID := *templatePoint.RelativeTo
	if relativePointID == id || depth > maxRecursionDepth {
		return nil, ErrRelativePointRecursion
	}

	relativePoint, err := p.getOrCreate(relativePointID, pat, depth)
	if err != nil {
		return nil, err
	}

	x, y, r, err := templatePoint.Position.evaluate(pat.Parameters(), p.Functions(pat))
	if err != nil {
		return nil, err
	}

	return point.NewRelativePoint(relativePoint).
		WithXOffset(x).WithYOffset(y).WithRotationOffset(r).
		MarkWith(id), nil
}

//nolint:ireturn,dupl
func (p Points) createBetween(id point.ID, pat *pattern.Pattern, depth int) (point.Point, error) {
	newPoint, ok := p[id]
	if !ok {
		return nil, ErrPointNotFound
	}

	if newPoint.Between.To == id || newPoint.Between.From == id || depth > maxRecursionDepth {
		return nil, ErrRelativePointRecursion
	}

	fromPoint, err := p.getOrCreate(newPoint.Between.From, pat, depth)
	if err != nil {
		return nil, err
	}

	toPoint, err := p.getOrCreate(newPoint.Between.To, pat, depth)
	if err != nil {
		return nil, err
	}

	params := pat.Parameters()

	offset, err := newPoint.Between.Offset.Evaluate(params, p.Functions(pat))
	if err != nil {
		return nil, err
	}

	return point.NewBetweenPoint(fromPoint, toPoint, offset, id), nil
}

//nolint:ireturn
func (p Points) getOrCreate(id point.ID, pat *pattern.Pattern, depth int) (point.Point, error) {
	if pat.GetPoint(id) == nil {
		err := p.addSingleToPattern(id, pat, depth+1)
		if err != nil {
			return nil, err
		}
	}

	createdPoint := pat.GetPoint(id)
	if createdPoint == nil {
		panic("getPoint cannot be nil")
	}

	return createdPoint, nil
}

//nolint:ireturn,dupl
func (p Points) createExtend(id point.ID, pat *pattern.Pattern, depth int) (point.Point, error) {
	newPoint, ok := p[id]
	if !ok {
		return nil, ErrPointNotFound
	}

	if newPoint.Extend.To == id || newPoint.Extend.From == id || depth > maxRecursionDepth {
		return nil, ErrRelativePointRecursion
	}

	fromPoint, err := p.getOrCreate(newPoint.Extend.From, pat, depth)
	if err != nil {
		return nil, err
	}

	toPoint, err := p.getOrCreate(newPoint.Extend.To, pat, depth)
	if err != nil {
		return nil, err
	}

	params := pat.Parameters()

	offset, err := newPoint.Extend.Offset.Evaluate(params, p.Functions(pat))
	if err != nil {
		return nil, err
	}

	return point.NewExtendPoint(fromPoint, toPoint, offset, id), nil
}

//nolint:ireturn
func (p Points) createPolar(id point.ID, pat *pattern.Pattern, depth int) (point.Point, error) {
	templatePoint, ok := p[id]
	if !ok {
		return nil, ErrPointNotFound
	}

	relativePointID := *templatePoint.RelativeTo
	if relativePointID == id || depth > maxRecursionDepth {
		return nil, ErrRelativePointRecursion
	}

	relativePoint, err := p.getOrCreate(relativePointID, pat, depth)
	if err != nil {
		return nil, err
	}

	x, y, err := templatePoint.Polar.evaluate(pat.Parameters(), p.Functions(pat))
	if err != nil {
		return nil, err
	}

	return point.NewRelativePoint(relativePoint).
		WithXOffset(x).WithYOffset(y).MarkWith(id), nil
}

// ExtendPoint describes how to draw a new point that extends in line with two points.
type ExtendPoint struct {
	From   point.ID `yaml:"from"`
	To     point.ID `yaml:"to"`
	Offset *Value   `yaml:"offset"`
}

// PolarPoint describes how to draw a new point with a direction and a distance from the current
// position.
type PolarPoint struct {
	Length   *Value `yaml:"length"`
	Rotation *Value `yaml:"rotation"`
}

func (p PolarPoint) evaluate(
	params govaluate.MapParameters,
	funcs map[string]govaluate.ExpressionFunction,
) (x, y float64, err error) {
	rotation, err := p.Rotation.Evaluate(params, funcs)
	if err != nil {
		return 0, 0, err
	}

	length, err := p.Length.Evaluate(params, funcs)
	if err != nil {
		return 0, 0, err
	}

	return math.Sin(rotation) * -length, math.Cos(rotation) * -length, nil
}