import gleam/list
import gleam/float
import gleam/int

pub type SketchStroke {
  SketchStroke(
    points: List(#(Float, Float)),
    color: String,
    thickness: Float,
    timestamp: String,
  )
}

pub type GhostWritingSession {
  GhostWritingSession(
    session_id: String,
    reference_image: String,
    user_strokes: List(SketchStroke),
    ghost_image_opacity: Float,
    current_page: Int,
    total_pages: Int,
  )
}

pub type SimilarityScore {
  SimilarityScore(
    overall_score: Float,
    structural_accuracy: Float,
    proportional_accuracy: Float,
    detail_completeness: Float,
    feedback: List(String),
  )
}

pub fn start_ghost_writing_session(
  image_url: String,
) -> GhostWritingSession {
  GhostWritingSession(
    session_id: "SESSION_2026",
    reference_image: image_url,
    user_strokes: [],
    ghost_image_opacity: 0.3,
    current_page: 1,
    total_pages: 1,
  )
}

pub fn create_stroke(
  points: List(#(Float, Float)),
  color: String,
  thickness: Float,
) -> SketchStroke {
  SketchStroke(
    points: points,
    color: color,
    thickness: thickness,
    timestamp: "2026-03-19T00:00:00Z",
  )
}

pub fn add_stroke_to_session(
  session: GhostWritingSession,
  stroke: SketchStroke,
) -> GhostWritingSession {
  GhostWritingSession(
    ..session,
    user_strokes: [stroke, ..session.user_strokes],
  )
}

pub fn adjust_ghost_opacity(
  session: GhostWritingSession,
  opacity: Float,
) -> GhostWritingSession {
  let clamped_opacity = case opacity {
    o if o <. 0.0 -> 0.0
    o if o >. 1.0 -> 1.0
    o -> o
  }
  GhostWritingSession(..session, ghost_image_opacity: clamped_opacity)
}

pub fn calculate_similarity(
  user_drawing: List(SketchStroke),
  _reference_image: String,
) -> SimilarityScore {
  let stroke_count = list.length(user_drawing)

  let structural_accuracy = case stroke_count {
    c if c > 15 -> 85.0
    c if c > 8 -> 65.0
    c if c > 3 -> 45.0
    _ -> 20.0
  }

  let proportional_accuracy = case stroke_count {
    c if c > 10 -> 80.0
    _ -> 50.0
  }

  let detail_completeness = case stroke_count {
    c if c > 15 -> 90.0
    c if c > 8 -> 70.0
    _ -> 40.0
  }

  let overall =
    {structural_accuracy +. proportional_accuracy +. detail_completeness} /. 3.0

  SimilarityScore(
    overall_score: overall,
    structural_accuracy: structural_accuracy,
    proportional_accuracy: proportional_accuracy,
    detail_completeness: detail_completeness,
    feedback: generate_drawing_feedback(overall, stroke_count),
  )
}

fn generate_drawing_feedback(score: Float, stroke_count: Int) -> List(String) {
  let base_feedback = case score {
    s if s >. 85.0 -> [
      "🏆 Exceptional job! Your drawing matches the reference perfectly!",
      "Your spatial understanding is excellent.",
    ]
    s if s >. 70.0 -> [
      "💪 Great work! Your sketch is very accurate.",
      "Minor details could be refined.",
    ]
    s if s >. 50.0 -> [
      "📈 Good effort! The main structure is recognizable.",
      "Try adding more detail.",
    ]
    _ -> [
      "Keep practicing! Reference the ghost image more carefully.",
      "Add more strokes to complete the drawing.",
    ]
  }

  case stroke_count {
    c if c < 3 ->
      list.append(base_feedback, ["Remember: Draw more strokes for better results!"])
    _ -> base_feedback
  }
}

pub fn generate_comparison_visualization(
  user_drawing: List(SketchStroke),
  _reference_image: String,
) -> String {
  let canvas = "<canvas id='comparison' width='800' height='600'></canvas>"
  let user_svg = render_strokes(user_drawing)
  "<div class='ghost-comparison'>" <> canvas <> user_svg <> "</div>"
}

fn render_strokes(strokes: List(SketchStroke)) -> String {
  "<svg class='user-drawing' width='800' height='600'>" <>
  list.fold(strokes, "", fn(acc, stroke) {
    acc <> render_stroke(stroke)
  }) <>
  "</svg>"
}

fn render_stroke(stroke: SketchStroke) -> String {
  case stroke.points {
    [] -> ""
    [first, ..rest] -> {
      let #(x, y) = first
      let path_start =
        "M " <> float.to_string(x) <> " " <> float.to_string(y)
      let path_rest =
        list.fold(rest, "", fn(acc, point) {
          let #(px, py) = point
          acc <> " L " <> float.to_string(px) <> " " <> float.to_string(py)
        })
      "<path d='" <>
      path_start <>
      path_rest <>
      "' stroke='" <>
      stroke.color <>
      "' stroke-width='" <>
      float.to_string(stroke.thickness) <>
      "' fill='none' stroke-linecap='round' />"
    }
  }
}

pub fn export_drawing_as_image(strokes: List(SketchStroke)) -> String {
  // Would generate PNG in production
  render_strokes(strokes)
}

pub fn compare_drawings(
  drawing1: List(SketchStroke),
  drawing2: List(SketchStroke),
) -> Float {
  // Simplified similarity metric
  let denominator =
    int.max(
      list.length(drawing1),
      list.length(drawing2),
    )

  case denominator == 0 {
    True -> 0.0
    False ->
      int.to_float(
        int.min(
          list.length(drawing1),
          list.length(drawing2),
        ),
      ) /. int.to_float(denominator) *. 100.0
  }
}

pub fn suggest_next_diagram(
  user_level: Float,
) -> String {
  case user_level {
    l if l >. 85.0 ->
      "Next: Advanced Anatomy (Heart Cross-Section)"
    l if l >. 70.0 ->
      "Next: Intermediate Diagram (Chemical Structure)"
    l if l >. 50.0 ->
      "Next: Basic Sketch (Simple Geometric Shape)"
    _ ->
      "Practice more with simpler diagrams first."
  }
}

pub fn track_drawing_history(session: GhostWritingSession) -> String {
  let stroke_count = list.length(session.user_strokes)
  "Drawing Progress: " <>
  int.to_string(stroke_count) <>
  " strokes | Page " <>
  int.to_string(session.current_page) <>
  "/" <>
  int.to_string(session.total_pages)
}

pub fn create_drawing_canvas_html() -> String {
  "
  <div class='ghost-writing-container'>
    <div class='ghost-layer'>
      <img id='ghostImg' src='' alt='Reference' class='ghost-image' />
      <canvas id='drawingCanvas' width='800' height='600' class='drawing-canvas'></canvas>
    </div>
    <div class='controls'>
      <label>Ghost Opacity: <input type='range' id='opacitySlider' min='0' max='100' value='30'></label>
      <button onclick='undoStroke()'>Undo</button>
      <button onclick='clearDrawing()'>Clear</button>
      <button onclick='submitDrawing()'>Submit</button>
    </div>
    <div id='feedback' class='feedback'></div>
  </div>"
}

pub fn analyze_drawing_curves(strokes: List(SketchStroke)) -> String {
  let smoothness =
    list.fold(strokes, 0.0, fn(acc, stroke) {
      acc +. calculate_curve_smoothness(stroke.points)
    }) /. int.to_float(list.length(strokes))

  "Curve Analysis: " <>
  float.to_string(smoothness) <>
  "% smoothness"
}

fn calculate_curve_smoothness(points: List(#(Float, Float))) -> Float {
  // Simplified - would use actual curvature analysis
  case list.length(points) {
    n if n > 10 -> 85.0
    n if n > 5 -> 70.0
    _ -> 50.0
  }
}

pub fn get_tracing_hints(
  _reference_image: String,
  current_progress: Float,
) -> List(String) {
  case current_progress {
    p if p <. 30.0 -> [
      "💡 Start by outlining the basic shape",
      "Focus on the main contours first",
    ]
    p if p <. 70.0 -> [
      "💡 Add the internal structures",
      "Pay attention to proportions",
    ]
    _ -> [
      "💡 Refine details and shading",
      "Your sketch looks great!",
    ]
  }
}