package datasources

import (
	"errors"
	"io/ioutil"
	"path/filepath"
	"strings"

	"github.com/grafana/grafana/pkg/bus"

	"github.com/grafana/grafana/pkg/log"

	"github.com/grafana/grafana/pkg/models"
	yaml "gopkg.in/yaml.v2"
)

var (
	ErrInvalidConfigToManyDefault = errors.New("datasource.yaml config is invalid. Only one datasource can be marked as default")
)

func Provision(configDirectory string) error {
	dc := newDatasourceProvisioner(log.New("provisioning.datasources"))
	return dc.applyChanges(configDirectory)
}

type DatasourceProvisioner struct {
	log         log.Logger
	cfgProvider *configReader
}

func newDatasourceProvisioner(log log.Logger) DatasourceProvisioner {
	return DatasourceProvisioner{
		log:         log,
		cfgProvider: &configReader{log: log},
	}
}

func (dc *DatasourceProvisioner) apply(cfg *DatasourcesAsConfig) error {
	if err := dc.deleteDatasources(cfg.DeleteDatasources); err != nil {
		return err
	}

	for _, ds := range cfg.Datasources {
		cmd := &models.GetDataSourceByNameQuery{OrgId: ds.OrgId, Name: ds.Name}
		err := bus.Dispatch(cmd)
		if err != nil && err != models.ErrDataSourceNotFound {
			return err
		}

		if err == models.ErrDataSourceNotFound {
			dc.log.Info("inserting datasource from configuration ", "name", ds.Name)
			insertCmd := createInsertCommand(ds)
			if err := bus.Dispatch(insertCmd); err != nil {
				return err
			}
		} else {
			dc.log.Debug("updating datasource from configuration", "name", ds.Name)
			updateCmd := createUpdateCommand(ds, cmd.Result.Id)
			if err := bus.Dispatch(updateCmd); err != nil {
				return err
			}
		}
	}

	return nil
}

func (dc *DatasourceProvisioner) applyChanges(configPath string) error {
	configs, err := dc.cfgProvider.readConfig(configPath)
	if err != nil {
		return err
	}

	for _, cfg := range configs {
		if err := dc.apply(cfg); err != nil {
			return err
		}
	}

	return nil
}

func (dc *DatasourceProvisioner) deleteDatasources(dsToDelete []*DeleteDatasourceConfig) error {
	for _, ds := range dsToDelete {
		cmd := &models.DeleteDataSourceByNameCommand{OrgId: ds.OrgId, Name: ds.Name}
		if err := bus.Dispatch(cmd); err != nil {
			return err
		}

		if cmd.DeletedDatasourcesCount > 0 {
			dc.log.Info("deleted datasource based on configuration", "name", ds.Name)
		}
	}

	return nil
}

type configReader struct {
	log log.Logger
}

func (cr *configReader) readConfig(path string) ([]*DatasourcesAsConfig, error) {
	var datasources []*DatasourcesAsConfig

	files, err := ioutil.ReadDir(path)
	if err != nil {
		cr.log.Error("cant read datasource provisioning files from directory", "path", path)
		return datasources, nil
	}

	for _, file := range files {
		if strings.HasSuffix(file.Name(), ".yaml") || strings.HasSuffix(file.Name(), ".yml") {
			filename, _ := filepath.Abs(filepath.Join(path, file.Name()))
			yamlFile, err := ioutil.ReadFile(filename)

			if err != nil {
				return nil, err
			}
			var datasource *DatasourcesAsConfig
			err = yaml.Unmarshal(yamlFile, &datasource)
			if err != nil {
				return nil, err
			}

			if datasource != nil {
				datasources = append(datasources, datasource)
			}
		}
	}

	defaultCount := 0
	for i := range datasources {
		if datasources[i].Datasources == nil {
			continue
		}

		for _, ds := range datasources[i].Datasources {
			if ds.OrgId == 0 {
				ds.OrgId = 1
			}

			if ds.IsDefault {
				defaultCount++
				if defaultCount > 1 {
					return nil, ErrInvalidConfigToManyDefault
				}
			}
		}

		for _, ds := range datasources[i].DeleteDatasources {
			if ds.OrgId == 0 {
				ds.OrgId = 1
			}
		}
	}

	return datasources, nil
}