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SassMeister-input.scss

// ----
// Sass (v3.4.1)
// Compass (v1.0.1)
// ----

// The idea is to provide some kind of friendly API to log stuff in Sass,
// including a way to log different type of messages (warnings, errors...).
// This is obviously mainly aimed at framework and library developers.
//
// Current implementation provides:
// - 5 levels of logging ("DEBUG" "INFO" "WARN" "ERROR" "FATAL");
// - a minimum level at which the logger starts printing;
// - an history of all logs, that can be printed as CSS;
// - a friendly API with easy-to-use functions;
// - a helper to learn more about different levels of logging.
//
// Also note that SassMeister doesn't show `@warn` but this code
// would print content in the console in a regular environment.
// 
// Feel free to do whatever you want with this.





// Instanciate a logger.
// This should be called once only.
//
// @param {String} minimum-level - Level at which the logger starts printing. Use `OFF` to disable.
// @requires {function} logger-conf
// @output Nothing, it just creates a global configuration map.
//
// @example scss - Instanciate a new logger logging INFO and up.
//  @include logger("INFO");
@mixin logger($minimum-level) {
  // Create global variable
  $logger-configuration: (
    "levels"  : "DEBUG" "INFO" "WARN" "ERROR" "FATAL",
    "errors"  : "FATAL" "ERROR",
    "min"     : $minimum-level,
    "history" : (
      "DEBUG" : (),
      "INFO"  : (),
      "WARN"  : (),
      "ERROR" : (),
      "FATAL" : ()
    )
  ) !global;
  
  // Cache "min-level" in the global map to improve performance
  $logger-configuration: map-merge($logger-configuration, 
    ("min-level": index(logger-conf("levels"), logger-conf("min")))
  ) !global;  
}





// Helper to get a key from `$logger-configuration` map.
//
// @access private
// @param {String} $key - Option to get from map
// @requires $logger-configuration
// @return {*} Option from `$logger-configuration` or `null` if `$key` doesn't exist.
// 
// @example scss - Get history from configuration map
// $history: logger-conf("history");
@function logger-conf($key) {
  @return map-get($logger-configuration, $key);
}





// Log a new `$message` with `$level`.
//
// @access private
// @param {String} $level - Message's level
// @param {String} $message - Message to log
// @requires {function} logger-conf
// @requires {mixin} logger-update-history
// @output Nothing, but warn/error in the console
// 
// @example scss - Log a new error.
//  @include log("ERROR", "Something's wrong.");
@mixin log($level, $message) {
  // If no logger has been instanciated, create one
  @if not global-variable-exists("logger-configuration") {
    @include logger("INFO");
  }
  
  $level: to-upper-case($level);
  
  // Unless it's disabled, proceed
  @if $level != "OFF" {
    // Get current level's index
    $index-current-level: index(logger-conf("levels"), $level);
    
    // If `$level` is invalid, falls back on `INFO`
    @if not $index-current-level { $level: "INFO" }
    
    // Update logger history
    @include logger-update-history($level, $message);
    
    // Finally, print message in console if current level is over minimum level
    @if $index-current-level >= logger-conf("min-level") {
      $print: $level + " :: " + $message;
  
      // `@error` if it's an error level
      @if index(logger-conf("errors"), $level) {
        @error #{$print};
      }
      
      // Else `@warn`
      @else {
        @warn #{$print};
      }
    }
  }
}

// A couple of shortcuts for `log` mixin.
@mixin FATAL($message) { @include log("FATAL", $message); }
@mixin ERROR($message) { @include log("ERROR", $message); }
@mixin  WARN($message) { @include log("WARN",  $message); }
@mixin  INFO($message) { @include log("INFO",  $message); }
@mixin DEBUG($message) { @include log("DEBUG", $message); }





// Update logger history
//
// @access private
// @param {String} $level - Message's level
// @param {String} $message - Message to log
// @requires {function} logger-conf
// @requires $logger-configuration
// @output Nothing
//
// @example scss - Update logger history with new entry
//  @include logger-update-history($level, $message);
@mixin logger-update-history($level, $message) {
  $history: logger-conf("history");
  $current-level-history: map-get($history, $level);
  $current-level-history: append($current-level-history, $message);
  $logger-history: map-merge($history, ($level: $current-level-history));
  $logger-configuration: map-merge($logger-configuration, ("history": $logger-history)) !global;
}

// Print logger history
//
// @requires logger-conf
// @output A `logger-logs` block
//
// @example scss - Print current logs.
//  @include logger-print-logs;
@mixin logger-print-logs {
  logger-logs {
    @each $level, $logs in logger-conf("history") {
      @if length($logs) > 0 {
        @each $log in $logs {
          #{$level}: $log;
        }
      }
    }
  }
}

// Print some extra informations about logger levels and what they mean
//
// @output A `logger-help` block
//
// @example scss - Print some extra help.
//  @include logger-help;
@mixin logger-help {
  logger-help {
    OFF: "Disable the logger.";
    FATAL: "Severe errors that cause premature termination.";
    ERROR: "Other runtime errors or unexpected conditions.";
    WARN: "Use of deprecated APIs, poor use of API, 'almost' errors,"
    + "other runtime situations that are undesirable or unexpected, but not necessarily wrong.";
    INFO: "Interesting runtime events (startup/shutdown).";
    DEBUG: "Detailed information on the flow through the system.";
  }
}





// EXAMPLE

// Instanciate a new logger,
// with "INFO" as the minimum level for logging.
// You can pass extra arguments as well.
// If you don't instanciate it yourself,
// it will be done automatically on first log.
@include logger("INFO");

// Logger help (optional, obviously)
@include logger-help;

// Log stuff
@include INFO("Hey, look at that.");
@include INFO("Bring in the unicorns!");
@include WARN("Dude, pay attention.");

// This one is not printed in the console but still tracked in logs.
@include DEBUG("Debug and stuff."); 

// Output history (optional),
// especially useful for debugging.
@include logger-print-logs;

SassMeister-output.css

logger-help {
  OFF: "Disable the logger.";
  FATAL: "Severe errors that cause premature termination.";
  ERROR: "Other runtime errors or unexpected conditions.";
  WARN: "Use of deprecated APIs, poor use of API, 'almost' errors,other runtime situations that are undesirable or unexpected, but not necessarily wrong.";
  INFO: "Interesting runtime events (startup/shutdown).";
  DEBUG: "Detailed information on the flow through the system.";
}

logger-logs {
  DEBUG: "Debug and stuff.";
  INFO: "Hey, look at that.";
  INFO: "Bring in the unicorns!";
  WARN: "Dude, pay attention.";
}