#hackwaly/easing

#Overview

#Basic Usage

#Linear Easing

test "linear easing demo" {
  // Linear easing is the identity function
  inspect(@easing.ease_linear(0.0), content="0")
  inspect(@easing.ease_linear(0.5), content="0.5")
  inspect(@easing.ease_linear(1.0), content="1")
}

#Quadratic Easing

test "quadratic easing demo" {
  // Different curve shapes
  inspect(@easing.ease_quad_in(0.5), content="0.25")    // Accelerating
  inspect(@easing.ease_quad_out(0.5), content="0.75")   // Decelerating  
  inspect(@easing.ease_quad(0.5), content="0.5")        // In-out (default)
}

#Cubic Easing

test "cubic easing demo" {
  inspect(@easing.ease_cubic_in(0.5), content="0.125")
  inspect(@easing.ease_cubic_out(0.5), content="0.875")
  inspect(@easing.ease_cubic(0.5), content="0.5")
}

#Advanced Easing with Optional Parameters

#Polynomial Easing

test "polynomial easing with options" {
  // Default exponent is 3.0 (same as cubic)
  let default_poly = @easing.ease_poly_in(0.5)
  inspect(default_poly, content="0.125")

  // Using direct function call with custom exponent
  let quadratic = @easing.poly_in(0.5, exponent=2.0)
  inspect(quadratic, content="0.25")

  let quartic = @easing.poly_in(0.5, exponent=4.0)
  inspect(quartic, content="0.0625")
}

#Back Easing with Custom Overshoot

test "back easing with custom overshoot" {
  // Default overshoot
  let normal_back = @easing.ease_back_in(0.5)

  // Custom overshoot for more dramatic effect
  let strong_back = @easing.back_in(0.5, overshoot=3.0)
  let weak_back = @easing.back_in(0.5, overshoot=1.0)

  // Stronger overshoot creates more negative values
  inspect(strong_back < normal_back, content="true")
  inspect(normal_back < weak_back, content="true")
}

#Elastic Easing with Custom Parameters

test "elastic easing with custom parameters" {
  // Default parameters
  let default_elastic = @easing.ease_elastic_in(0.5)

  // Custom amplitude affects oscillation strength
  let strong_elastic = @easing.elastic_in(0.5, amplitude=2.0)
  inspect(default_elastic != strong_elastic, content="true")

  // Custom period affects oscillation frequency  
  let fast_oscillation = @easing.elastic_in(0.5, period=0.1)
  let slow_oscillation = @easing.elastic_in(0.5, period=0.8)
  inspect(fast_oscillation != slow_oscillation, content="true")
}

#Specialized Easing Functions

#Exponential Easing

test "exponential easing characteristics" {
  // Values change rapidly near the extremes
  let exp_early = @easing.ease_exp_in(0.1)
  let exp_late = @easing.ease_exp_in(0.9)

  // Early values are very small
  inspect(exp_early < 0.01, content="true")
  // Later values grow but slowly at first
  inspect(exp_late < 1.0, content="true")
}

#Bounce Easing

test "bounce easing behavior" {
  // Bounce typically overshoots during animation
  let quarter_bounce = @easing.ease_bounce_out(0.25)
  let half_bounce = @easing.ease_bounce_out(0.5)

  // The bounce creates peaks above the linear progression
  inspect(quarter_bounce > 0.25, content="true")
  inspect(half_bounce > 0.5, content="true")
}

#Circle Easing

test "circle easing smoothness" {
  // Circle easing provides smooth curves
  inspect(@easing.ease_circle_in(0.0), content="0")
  inspect(@easing.ease_circle_out(1.0), content="1")
  inspect(@easing.ease_circle(0.5), content="0.5")
}

#Sine Easing

test "sine easing curves" {
  // Sine creates very natural feeling motion
  let sin_quarter = @easing.ease_sin_in(0.25)
  let sin_half = @easing.ease_sin_out(0.5)

  // Values are between 0 and 1 with smooth transitions
  inspect(sin_quarter > 0.0 && sin_quarter < 0.25, content="true")
  inspect(sin_half > 0.5 && sin_half < 1.0, content="true")
}

#API Compatibility

test "API compatibility" {
  // Direct function calls (support optional parameters)
  let poly_custom = @easing.poly_in(0.5, exponent=2.0)
  let back_custom = @easing.back_out(0.5, overshoot=2.0)

  // Convenience aliases (d3-ease compatible names)
  let poly_default = @easing.ease_poly_in(0.5)
  let back_default = @easing.ease_back_out(0.5)

  // Verify the aliases work correctly
  inspect(@easing.ease_linear(0.5) == @easing.linear(0.5), content="true")
  inspect(poly_default, content="0.125") // Default exponent 3.0

  // Demonstrate usage
  ignore(poly_custom)
  ignore(back_custom)
  ignore(back_default)
}

#Function Categories

• Linear: ease_linear - Constant speed
• Quadratic: ease_quad_* - Gentle curves
• Cubic: ease_cubic_* - More pronounced curves
• Polynomial: ease_poly_* - Configurable exponent (supports exponent= parameter)
• Sine: ease_sin_* - Natural, smooth curves
• Exponential: ease_exp_* - Dramatic acceleration/deceleration
• Circle: ease_circle_* - Quarter-circle based curves
• Back: ease_back_* - Anticipation/overshoot (supports overshoot= parameter)
• Bounce: ease_bounce_* - Bouncing ball physics
• Elastic: ease_elastic_* - Spring/rubber band effects (supports amplitude= and period= parameters)

#Choosing the Right Easing

• Linear: Use for simple fades or when you want constant speed
• Quad/Cubic: Great for general UI transitions - natural but noticeable
• Sine: Excellent for organic, subtle animations
• Exponential: Use sparingly for dramatic impact
• Circle: Good balance of smoothness and visibility
• Back: Perfect for attention-grabbing effects with anticipation
• Elastic: Fun and playful - great for casual, game-like interfaces
• Bounce: Realistic physics simulation for ball-like objects