package config

import (
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"os"

	"github.com/ghodss/yaml"
	"github.com/pkg/errors"
)

// Config defines the structure of the config files
type Config struct {
	General map[string]interface{}            `json:"general"`
	Stages  map[string]map[string]interface{} `json:"stages"`
	Steps   map[string]map[string]interface{} `json:"steps"`
}

// StepConfig defines the structure for merged step configuration
type StepConfig struct {
	Config map[string]interface{}
}

// ReadConfig loads config and returns its content
func (c *Config) ReadConfig(configuration io.ReadCloser) error {
	defer configuration.Close()

	content, err := ioutil.ReadAll(configuration)
	if err != nil {
		return errors.Wrapf(err, "error reading %v", configuration)
	}

	err = yaml.Unmarshal(content, &c)
	if err != nil {
		return NewParseError(fmt.Sprintf("error unmarshalling %q: %v", content, err))
	}
	return nil
}

// GetStepConfig provides merged step configuration using defaults, config, if available
func (c *Config) GetStepConfig(flagValues map[string]interface{}, paramJSON string, configuration io.ReadCloser, defaults []io.ReadCloser, filters StepFilters, stageName, stepName string) (StepConfig, error) {
	var stepConfig StepConfig
	var d PipelineDefaults

	if err := c.ReadConfig(configuration); err != nil {
		switch err.(type) {
		case *ParseError:
			return StepConfig{}, errors.Wrap(err, "failed to parse custom pipeline configuration")
		default:
			//ignoring unavailability of config file since considered optional
		}
	}

	if err := d.ReadPipelineDefaults(defaults); err != nil {
		switch err.(type) {
		case *ParseError:
			return StepConfig{}, errors.Wrap(err, "failed to parse pipeline default configuration")
		default:
			//ignoring unavailability of defaults since considered optional
		}
	}

	// first: read defaults & merge general -> steps (-> general -> steps ...)
	for _, def := range d.Defaults {
		stepConfig.mixIn(def.General, filters.General)
		stepConfig.mixIn(def.Steps[stepName], filters.Steps)
	}

	// second: read config & merge - general -> steps -> stages
	stepConfig.mixIn(c.General, filters.General)
	stepConfig.mixIn(c.Steps[stepName], filters.Steps)
	stepConfig.mixIn(c.Stages[stageName], filters.Stages)

	// third: merge parameters provided via env vars
	stepConfig.mixIn(envValues(filters.All), filters.All)

	// fourth: if parameters are provided in JSON format merge them
	if len(paramJSON) != 0 {
		var params map[string]interface{}
		json.Unmarshal([]byte(paramJSON), &params)
		stepConfig.mixIn(params, filters.Parameters)
	}

	// fifth: merge command line flags
	if flagValues != nil {
		stepConfig.mixIn(flagValues, filters.Parameters)
	}

	return stepConfig, nil
}

// GetStepConfigWithJSON provides merged step configuration using a provided stepConfigJSON with additional flags provided
func GetStepConfigWithJSON(flagValues map[string]interface{}, stepConfigJSON string, filters StepFilters) StepConfig {
	var stepConfig StepConfig

	stepConfigMap := map[string]interface{}{}

	json.Unmarshal([]byte(stepConfigJSON), &stepConfigMap)

	stepConfig.mixIn(stepConfigMap, filters.All)

	// ToDo: mix in parametersJSON

	if flagValues != nil {
		stepConfig.mixIn(flagValues, filters.Parameters)
	}
	return stepConfig
}

// GetJSON returns JSON representation of an object
func GetJSON(data interface{}) (string, error) {

	result, err := json.Marshal(data)
	if err != nil {
		return "", errors.Wrapf(err, "error marshalling json: %v", err)
	}
	return string(result), nil
}

func envValues(filter []string) map[string]interface{} {
	vals := map[string]interface{}{}
	for _, param := range filter {
		if envVal := os.Getenv("PIPER_" + param); len(envVal) != 0 {
			vals[param] = os.Getenv("PIPER_" + param)
		}
	}
	return vals
}

func (s *StepConfig) mixIn(mergeData map[string]interface{}, filter []string) {

	if s.Config == nil {
		s.Config = map[string]interface{}{}
	}

	s.Config = filterMap(merge(s.Config, mergeData), filter)
}

func filterMap(data map[string]interface{}, filter []string) map[string]interface{} {
	result := map[string]interface{}{}

	if data == nil {
		data = map[string]interface{}{}
	}

	for key, value := range data {
		if len(filter) == 0 || sliceContains(filter, key) {
			result[key] = value
		}
	}
	return result
}

func merge(base, overlay map[string]interface{}) map[string]interface{} {

	result := map[string]interface{}{}

	if base == nil {
		base = map[string]interface{}{}
	}

	for key, value := range base {
		result[key] = value
	}

	for key, value := range overlay {
		if val, ok := value.(map[string]interface{}); ok {
			if valBaseKey, ok := base[key].(map[string]interface{}); !ok {
				result[key] = merge(map[string]interface{}{}, val)
			} else {
				result[key] = merge(valBaseKey, val)
			}
		} else {
			result[key] = value
		}
	}
	return result
}

func sliceContains(slice []string, find string) bool {
	for _, elem := range slice {
		if elem == find {
			return true
		}
	}
	return false
}