package planr

import (
  // "fmt"
  "log"
  "github.com/BurntSushi/toml"
)


/*
  TODO: Every property defined within the defaults currently 
  has to implement the "inherit" method to conditionally inherit a
  property in relation to a parent. (Ostensibly so that test cases
  can override default configuration.) This is pedantic because 
  most properties will end up writing boilerplate amounting to:

  parent.inherit()
  ...
  if config.property == nil {
    config.property = config.parent.property
  }

  This library provides copying behavior between structs
  with common properties using reflection. It seems like
  a slight abuse of reflection... But, it could be 
  retro-fitted to implement this behavior if a "onlyCopyZeroFields"
  option was provided.

  > "github.com/jinzhu/copier"
*/

// Inheritable configuration can inherit properties defined in a
// defaults file. This happens on a per-directory basis so multiple
// tests can share common configuration.
//
// The parent will always be of the same type as the child and an
// assertion is required to define the proper behavior.
type InheritableConfig interface {
  Inherit(parent interface{})
}

// A parser function takes a blob of TOML and decodes it into
// configuration relevant to an adapter
type TomlParser func (toml.Primitive) InheritableConfig

// The name under which an adapter registers corresponds
// to a table under the super-table adapters. All corresponding
// TOML will be passed to the ParseConfig method or ParseDefaultConfig
// for parsing. The ParseConfig file parses options in test case files.
// The ParseDefaultConfig is parsed by `defaults.toml` files and can
// be used to establish default configuration that will be inherited
// by all units in a common directory (collection)
type AdapterConfig struct {
   Name                string
   ParseConfig         TomlParser
   ParseDefaultConfig  TomlParser
}

// Program-wide configuration which is recognized
// in defaults.toml
type Defaults struct {
  Points      *float32

  /*
    The TOML library only parses exported fields.
    The Adapters field is an intermediate mapping
    individual adapters to their locally defined
    configuration. After they individually process
    the configuration, it is mapped to the adapters_
    field.

    See: decodeAdapters()
  */
  Adapters    *map[string] toml.Primitive
  adapters_    map[string] InheritableConfig

  /*
    The configs_ field is necessary to property
    implement the Inherit method using a common
    interface. 
  */
  configs_    *[]AdapterConfig
}

// Program-wide testcase config
type TestCaseConfig struct {
  Defaults
  Title       *string
  Description *string
}

// The default configuration must be able in inherit from
// other defaults further up the tree
//
// This provides multiple levels of configurability
func (child *Defaults) Inherit(p interface{}) {
  parent := p.(Defaults)

  // Inherit properties which haven't been configured
  if child.Points == nil {
    child.Points = parent.Points;
  }

  // Call the inherit method as defined by the adapters
  // If an adapter is undefined, inherit the parent configuration
  //
  // _configs represents all adapters (registered to a runner)
  for _, adapter := range *child.configs_ {
    parent_adapter, parent_exists := parent.adapters_[adapter.Name]
    child_adapter,  child_exists  := child.adapters_[adapter.Name]

    if parent_exists {
      if child_exists {
        child_adapter.Inherit(parent_adapter)
      } else {
        child.adapters_[adapter.Name] = parent_adapter 
      }
    }
  }
}

// Parses the intermediate adapters Adapters containing TOML primitives 
// according to methods registered with the runner
// Once parsed, they are stored alongside the registered name to determine
// which adapter will receive the configuration
func (defaults *Defaults) decodeAdapters(adapters []AdapterConfig, asDefault bool) {
  defaults.configs_ = &adapters
  defaults.adapters_ = make(map[string]InheritableConfig)

  if defaults.Adapters != nil {
    for _, config := range adapters {
      primitive, exists := (*defaults.Adapters)[config.Name]
    
      if exists {
        var parsed InheritableConfig
        if asDefault {
          parsed = config.ParseDefaultConfig(primitive)
        } else {
          parsed = config.ParseConfig(primitive)
        }

        defaults.adapters_[config.Name] = parsed
      }
    }
  }
}

// Decode defaults.toml
func DecodeDefaults(path string, adapterCfg []AdapterConfig) Defaults {
  defaults := Defaults { }

  if _, err := toml.DecodeFile(path, &defaults); err != nil {
    log.Fatal(err)
  }

  defaults.decodeAdapters(adapterCfg, true)

  return defaults
}

// Decode an individual unit
func DecodeConfig(path string, adapterCfg []AdapterConfig) TestCaseConfig {
  config := TestCaseConfig { }

  if _, err := toml.DecodeFile(path, &config); err != nil {
    log.Fatal(err)
  }

  config.decodeAdapters(adapterCfg, false)

  return config
}