# Direct R Translation of Draradech's JavaScript Jigsaw Puzzle Generator
# Original source: https://gist.github.com/Draradech/35d36347312ca6d0887aa7d55f366e30
# License: CC0 (Public Domain)
#
# Optimized with batch RNG generation using C++ uniform_batch() when available.
# See R/rng_iterator.R for the batch optimization implementation.

# Global variables (matching JS implementation exactly)
.jigsaw_env <- new.env()

#' Initialize jigsaw environment with global variables
#' @param seed Random seed (default: random)
#' @param tabsize Tab size as percentage (0-100). Default: 6.
#' @param jitter Jitter percentage (default: 4)
#' @param width Puzzle width in mm (default: 300)
#' @param height Puzzle height in mm (default: 200)
#' @param unit Unit specification: "mm" or "px"
#' @param dpi DPI for conversion (default: 96)
#' @param radius Corner radius in mm (default: 2.0)
#' @param xn Number of columns (default: 15)
#' @param yn Number of rows (default: 10)
#' @param min_tab_size Minimum absolute tab size in mm (default: NULL for no limit).
#'   Prevents tabs from becoming too small on short edges.
#' @param max_tab_size Maximum absolute tab size in mm (default: NULL for no limit).
#'   Prevents tabs from becoming too large on long edges.
init_jigsaw <- function(seed = NULL, tabsize = 6, jitter = 4,
                        width = 300, height = 200,
                        unit = "mm", dpi = 96, radius = 2.0,
                        xn = 15, yn = 10,
                        min_tab_size = NULL, max_tab_size = NULL) {

  if (is.null(seed)) {
    seed <- as.integer(runif(1) * 10000)
  }

  # Store all parameters in environment
  .jigsaw_env$seed_initial <- seed
  .jigsaw_env$seed <- seed
  .jigsaw_env$tabsize <- tabsize
  .jigsaw_env$jitter <- jitter
  .jigsaw_env$width <- width
  .jigsaw_env$height <- height
  .jigsaw_env$unit <- unit
  .jigsaw_env$dpi <- dpi
  .jigsaw_env$radius <- radius
  .jigsaw_env$xn <- xn
  .jigsaw_env$yn <- yn
  .jigsaw_env$offset <- 0.0

  # Tab size constraints
  .jigsaw_env$min_tab_size <- min_tab_size
  .jigsaw_env$max_tab_size <- max_tab_size

  # Parse input (equivalent to parse_input() in JS)
  .jigsaw_env$t_base <- tabsize / 100.0  # Normalized: same formula as all puzzle types
  .jigsaw_env$t <- .jigsaw_env$t_base     # Effective t (may be adjusted per edge)
  .jigsaw_env$j <- jitter / 100.0

  # Create RNG iterator with pre-generated batch values for performance
  # This uses C++ uniform_batch() when available (~27x speedup)
  rng_count <- calc_rect_rng_count(xn, yn)
  .jigsaw_env$rng <- create_rng_iterator(seed, rng_count)
}

# Random number generator - uses pre-generated batch values
# (Original JS translation used per-call sine-based RNG)
random <- function() {
  .jigsaw_env$rng$next_val()
}

uniform <- function(min_val, max_val) {
  .jigsaw_env$rng$uniform(min_val, max_val)
}

rbool <- function() {
  .jigsaw_env$rng$rbool()
}

# Tab generation functions (exact JS translation)
first <- function() {
  .jigsaw_env$e <- uniform(-.jigsaw_env$j, .jigsaw_env$j)
  .jigsaw_env$flip <- NULL  # Initialize flip for first call
  next_tab()
}

next_tab <- function() {
  flipold <- if (exists("flip", envir = .jigsaw_env)) .jigsaw_env$flip else NULL
  .jigsaw_env$flip <- rbool()
  .jigsaw_env$a <- if (is.null(flipold) || .jigsaw_env$flip == flipold) -.jigsaw_env$e else .jigsaw_env$e
  .jigsaw_env$b <- uniform(-.jigsaw_env$j, .jigsaw_env$j)
  .jigsaw_env$c <- uniform(-.jigsaw_env$j, .jigsaw_env$j)
  .jigsaw_env$d <- uniform(-.jigsaw_env$j, .jigsaw_env$j)
  .jigsaw_env$e <- uniform(-.jigsaw_env$j, .jigsaw_env$j)

  # Apply min/max tab size constraints for this edge
  apply_tab_constraints()
}

#' Apply min/max tab size constraints for the current edge
#'
#' Adjusts .jigsaw_env$t based on the current edge length and any
#' min/max constraints. Called automatically by next_tab().
#'
#' Tab height formula: tab_height = 3 * t * edge_length
#' If min_tab_size would require a tab wider than 70% of the edge,
#' the maximum safe width is used instead.
#'
#' @keywords internal
apply_tab_constraints <- function() {
  # Skip if no constraints are set
  if (is.null(.jigsaw_env$min_tab_size) && is.null(.jigsaw_env$max_tab_size)) {
    .jigsaw_env$t <- .jigsaw_env$t_base
    return()
  }

  # Get current edge length
  edge_length <- sl()

  # Calculate current tab height using base t value
  tab_height <- 3.0 * .jigsaw_env$t_base * edge_length

  t <- .jigsaw_env$t_base

  # Apply minimum constraint
  if (!is.null(.jigsaw_env$min_tab_size) && tab_height < .jigsaw_env$min_tab_size) {
    t <- .jigsaw_env$min_tab_size / (3.0 * edge_length)

    # Check if this would make the tab too wide for the edge
    # Tab spans from 0.5 - 2t to 0.5 + 2t, so total width is 4t
    # It should fit within roughly 0.1 to 0.9 of the edge (leaving margins)
    if (4.0 * t > 0.7) {
      # Cap at maximum safe width
      t <- 0.175  # 0.7 / 4
    }
  }

  # Apply maximum constraint
  if (!is.null(.jigsaw_env$max_tab_size) && tab_height > .jigsaw_env$max_tab_size) {
    t <- .jigsaw_env$max_tab_size / (3.0 * edge_length)
  }

  .jigsaw_env$t <- t
}

# Coordinate calculation functions (exact JS translation)
sl <- function() {
  return(if (.jigsaw_env$vertical) .jigsaw_env$height / .jigsaw_env$yn else .jigsaw_env$width / .jigsaw_env$xn)
}

sw <- function() {
  return(if (.jigsaw_env$vertical) .jigsaw_env$width / .jigsaw_env$xn else .jigsaw_env$height / .jigsaw_env$yn)
}

ol <- function() {
  return(.jigsaw_env$offset + sl() * (if (.jigsaw_env$vertical) .jigsaw_env$yi else .jigsaw_env$xi))
}

ow <- function() {
  return(.jigsaw_env$offset + sw() * (if (.jigsaw_env$vertical) .jigsaw_env$xi else .jigsaw_env$yi))
}

l <- function(v) {
  ret <- ol() + sl() * v
  return(round(ret * 100) / 100)
}

w <- function(v) {
  ret <- ow() + sw() * v * (if (.jigsaw_env$flip) -1.0 else 1.0)
  return(round(ret * 100) / 100)
}

# Bézier control point functions (exact JS translation)
p0l <- function() l(0.0)
p0w <- function() w(0.0)
p1l <- function() l(0.2)
p1w <- function() w(.jigsaw_env$a)
p2l <- function() l(0.5 + .jigsaw_env$b + .jigsaw_env$d)
p2w <- function() w(-.jigsaw_env$t + .jigsaw_env$c)
p3l <- function() l(0.5 - .jigsaw_env$t + .jigsaw_env$b)
p3w <- function() w(.jigsaw_env$t + .jigsaw_env$c)
p4l <- function() l(0.5 - 2.0 * .jigsaw_env$t + .jigsaw_env$b - .jigsaw_env$d)
p4w <- function() w(3.0 * .jigsaw_env$t + .jigsaw_env$c)
p5l <- function() l(0.5 + 2.0 * .jigsaw_env$t + .jigsaw_env$b - .jigsaw_env$d)
p5w <- function() w(3.0 * .jigsaw_env$t + .jigsaw_env$c)
p6l <- function() l(0.5 + .jigsaw_env$t + .jigsaw_env$b)
p6w <- function() w(.jigsaw_env$t + .jigsaw_env$c)
p7l <- function() l(0.5 + .jigsaw_env$b + .jigsaw_env$d)
p7w <- function() w(-.jigsaw_env$t + .jigsaw_env$c)
p8l <- function() l(0.8)
p8w <- function() w(.jigsaw_env$e)
p9l <- function() l(1.0)
p9w <- function() w(0.0)

# Main generation functions (exact JS translation)
gen_dh <- function() {
  str <- ""
  .jigsaw_env$vertical <- 0

  for (yi in 1:(.jigsaw_env$yn - 1)) {
    .jigsaw_env$yi <- yi
    .jigsaw_env$xi <- 0
    first()
    str <- paste0(str, "M ", p0l(), ",", p0w(), " ")

    while (.jigsaw_env$xi < .jigsaw_env$xn) {
      str <- paste0(str, "C ", p1l(), " ", p1w(), " ", p2l(), " ", p2w(), " ", p3l(), " ", p3w(), " ")
      str <- paste0(str, "C ", p4l(), " ", p4w(), " ", p5l(), " ", p5w(), " ", p6l(), " ", p6w(), " ")
      str <- paste0(str, "C ", p7l(), " ", p7w(), " ", p8l(), " ", p8w(), " ", p9l(), " ", p9w(), " ")
      next_tab()
      .jigsaw_env$xi <- .jigsaw_env$xi + 1
    }
  }
  return(str)
}

gen_dv <- function() {
  str <- ""
  .jigsaw_env$vertical <- 1

  for (xi in 1:(.jigsaw_env$xn - 1)) {
    .jigsaw_env$xi <- xi
    .jigsaw_env$yi <- 0
    first()
    str <- paste0(str, "M ", p0w(), ",", p0l(), " ")

    while (.jigsaw_env$yi < .jigsaw_env$yn) {
      str <- paste0(str, "C ", p1w(), " ", p1l(), " ", p2w(), " ", p2l(), " ", p3w(), " ", p3l(), " ")
      str <- paste0(str, "C ", p4w(), " ", p4l(), " ", p5w(), " ", p5l(), " ", p6w(), " ", p6l(), " ")
      str <- paste0(str, "C ", p7w(), " ", p7l(), " ", p8w(), " ", p8l(), " ", p9w(), " ", p9l(), " ")
      next_tab()
      .jigsaw_env$yi <- .jigsaw_env$yi + 1
    }
  }
  return(str)
}

gen_db <- function() {
  offset <- .jigsaw_env$offset
  width <- .jigsaw_env$width
  height <- .jigsaw_env$height
  radius <- .jigsaw_env$radius

  str <- ""
  str <- paste0(str, "M ", (offset + radius), " ", (offset), " ")
  str <- paste0(str, "L ", (offset + width - radius), " ", (offset), " ")
  str <- paste0(str, "A ", (radius), " ", (radius), " 0 0 1 ", (offset + width), " ", (offset + radius), " ")
  str <- paste0(str, "L ", (offset + width), " ", (offset + height - radius), " ")
  str <- paste0(str, "A ", (radius), " ", (radius), " 0 0 1 ", (offset + width - radius), " ", (offset + height), " ")
  str <- paste0(str, "L ", (offset + radius), " ", (offset + height), " ")
  str <- paste0(str, "A ", (radius), " ", (radius), " 0 0 1 ", (offset), " ", (offset + height - radius), " ")
  str <- paste0(str, "L ", (offset), " ", (offset + radius), " ")
  str <- paste0(str, "A ", (radius), " ", (radius), " 0 0 1 ", (offset + radius), " ", (offset), " ")
  return(str)
}

#' Generate jigsaw puzzle SVG (main function)
#' @param seed Random seed
#' @param tabsize Tab size as percentage (0-100). Default: 6.
#' @param jitter Jitter percentage (0-13)
#' @param width Puzzle width in mm
#' @param height Puzzle height in mm
#' @param unit Measurement unit (default "mm")
#' @param dpi Resolution in dots per inch (default 96)
#' @param radius Corner radius in mm
#' @param xn Number of columns
#' @param yn Number of rows
#' @return List containing SVG path data
generate_jigsaw_svg <- function(seed = NULL, tabsize = 6, jitter = 4,
                                width = 300, height = 200, 
                                unit = "mm", dpi = 96, radius = 2.0,
                                xn = 15, yn = 10) {

  # Convert to mm for internal calculations if needed
  if (unit == "px") {
    width_mm <- width * 25.4 / dpi
    height_mm <- height * 25.4 / dpi
    radius_mm <- radius * 25.4 / dpi
  } else {
    width_mm <- width
    height_mm <- height
    radius_mm <- radius
  }

  # Initialize environment
  init_jigsaw(seed, tabsize, jitter, width_mm, height_mm, unit, dpi, radius_mm, xn, yn)

  # Generate path data
  horizontal_paths <- gen_dh()
  vertical_paths <- gen_dv()
  border_paths <- gen_db()

  # Create SVG dimensions based on unit and DPI
  if (unit == "px") {
    svg_width <- sprintf("%.0f", width)
    svg_height <- sprintf("%.0f", height)
    # ViewBox uses mm units for consistency in path coordinates
    viewbox_w <- width_mm
    viewbox_h <- height_mm
  } else {
    svg_width <- sprintf("%.0fmm", width)
    svg_height <- sprintf("%.0fmm", height)
    viewbox_w <- width
    viewbox_h <- height
  }

  # Create complete SVG
  svg_content <- paste0(
    '<svg xmlns="http://www.w3.org/2000/svg" version="1.0" ',
    'width="', svg_width, '" height="', svg_height, '" ',
    'viewBox="0 0 ', viewbox_w, ' ', viewbox_h, '">',
    '<path fill="none" stroke="DarkBlue" stroke-width="0.1" d="',
    horizontal_paths,
    '"></path>',
    '<path fill="none" stroke="DarkRed" stroke-width="0.1" d="',
    vertical_paths,
    '"></path>',
    '<path fill="none" stroke="Black" stroke-width="0.1" d="',
    border_paths,
    '"></path>',
    '</svg>'
  )

  return(list(
    svg = svg_content,
    horizontal = horizontal_paths,
    vertical = vertical_paths,
    border = border_paths,
    parameters = list(
      seed = .jigsaw_env$seed_initial,
      tabsize = tabsize,
      jitter = jitter,
      width = width,
      height = height,
      unit = unit,
      dpi = dpi,
      width_mm = width_mm,
      height_mm = height_mm,
      radius = radius,
      xn = xn,
      yn = yn
    )
  ))
}

#' Save SVG to file
#' @param puzzle_data Output from generate_jigsaw_svg()
#' @param filename Output filename (default: "jigsaw.svg")
save_jigsaw_svg <- function(puzzle_data, filename = "jigsaw.svg") {
  # Ensure parent directory exists
  output_parent <- dirname(filename)
  if (nzchar(output_parent) && output_parent != "." && !dir.exists(output_parent)) {
    dir.create(output_parent, recursive = TRUE)
  }

  writeLines(puzzle_data$svg, filename)
  log_success("Saved jigsaw puzzle to: {.file {filename}}")
}

#' Print puzzle parameters
#' @param puzzle_data Output from generate_jigsaw_svg()
print_puzzle_info <- function(puzzle_data) {
  params <- puzzle_data$parameters
  log_subheader("Jigsaw Puzzle Parameters")
  log_params("Puzzle Configuration", list(
    Seed = params$seed,
    Size = paste0(params$width, " x ", params$height, " mm"),
    Pieces = paste0(params$xn, " x ", params$yn, " = ", params$xn * params$yn, " total"),
    "Tab size" = paste0(params$tabsize, "%"),
    Jitter = paste0(params$jitter, "%"),
    "Corner radius" = paste0(params$radius, " mm")
  ))
}

# Note: Example usage moved to inst/examples/rectangular_puzzle_example.R
# to avoid auto-execution when sourcing this file for function definitions