package graphite

import (
	"fmt"
	"strings"

	"github.com/influxdata/influxdb/models"
)

const (
	// DefaultBindAddress is the default binding interface if none is specified.
	DefaultBindAddress = ":2003"

	// DefaultDatabase is the default database if none is specified.
	DefaultDatabase = "graphite"

	// DefaultProtocol is the default IP protocol used by the Graphite input.
	DefaultProtocol = "tcp"

	// DefaultSeparator is the default join character to use when joining multiple
	// measurment parts in a template.
	DefaultSeparator = "."

	// DefaultUDPReadBuffer is the default buffer size for the UDP listener.
	// Sets the size of the operating system's receive buffer associated with
	// the UDP traffic. Keep in mind that the OS must be able
	// to handle the number set here or the UDP listener will error and exit.
	//
	// DefaultReadBuffer = 0 means to use the OS default, which is usually too
	// small for high UDP performance.
	//
	// Increasing OS buffer limits:
	//     Linux:      sudo sysctl -w net.core.rmem_max=<read-buffer>
	//     BSD/Darwin: sudo sysctl -w kern.ipc.maxsockbuf=<read-buffer>
	DefaultUdpReadBuffer = 0
)

// Config represents the configuration for Graphite endpoints.
type Config struct {
	BindAddress   string
	Protocol      string
	UdpReadBuffer int
	Separator     string
	Tags          []string
	Templates     []string
}

// WithDefaults takes the given config and returns a new config with any required
// default values set.
func (c *Config) WithDefaults() *Config {
	d := *c
	if d.BindAddress == "" {
		d.BindAddress = DefaultBindAddress
	}
	if d.Protocol == "" {
		d.Protocol = DefaultProtocol
	}
	if d.Separator == "" {
		d.Separator = DefaultSeparator
	}
	if d.UdpReadBuffer == 0 {
		d.UdpReadBuffer = DefaultUdpReadBuffer
	}
	return &d
}

// DefaultTags returns the config's tags.
func (c *Config) DefaultTags() models.Tags {
	tags := models.Tags{}
	for _, t := range c.Tags {
		parts := strings.Split(t, "=")
		tags[parts[0]] = parts[1]
	}
	return tags
}

// Validate validates the config's templates and tags.
func (c *Config) Validate() error {
	if err := c.validateTemplates(); err != nil {
		return err
	}

	if err := c.validateTags(); err != nil {
		return err
	}

	return nil
}

func (c *Config) validateTemplates() error {
	// map to keep track of filters we see
	filters := map[string]struct{}{}

	for i, t := range c.Templates {
		parts := strings.Fields(t)
		// Ensure template string is non-empty
		if len(parts) == 0 {
			return fmt.Errorf("missing template at position: %d", i)
		}
		if len(parts) == 1 && parts[0] == "" {
			return fmt.Errorf("missing template at position: %d", i)
		}

		if len(parts) > 3 {
			return fmt.Errorf("invalid template format: '%s'", t)
		}

		template := t
		filter := ""
		tags := ""
		if len(parts) >= 2 {
			// We could have <filter> <template>  or <template> <tags>.  Equals is only allowed in
			// tags section.
			if strings.Contains(parts[1], "=") {
				template = parts[0]
				tags = parts[1]
			} else {
				filter = parts[0]
				template = parts[1]
			}
		}

		if len(parts) == 3 {
			tags = parts[2]
		}

		// Validate the template has one and only one measurement
		if err := c.validateTemplate(template); err != nil {
			return err
		}

		// Prevent duplicate filters in the config
		if _, ok := filters[filter]; ok {
			return fmt.Errorf("duplicate filter '%s' found at position: %d", filter, i)
		}
		filters[filter] = struct{}{}

		if filter != "" {
			// Validate filter expression is valid
			if err := c.validateFilter(filter); err != nil {
				return err
			}
		}

		if tags != "" {
			// Validate tags
			for _, tagStr := range strings.Split(tags, ",") {
				if err := c.validateTag(tagStr); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

func (c *Config) validateTags() error {
	for _, t := range c.Tags {
		if err := c.validateTag(t); err != nil {
			return err
		}
	}
	return nil
}

func (c *Config) validateTemplate(template string) error {
	hasMeasurement := false
	for _, p := range strings.Split(template, ".") {
		if p == "measurement" || p == "measurement*" {
			hasMeasurement = true
		}
	}

	if !hasMeasurement {
		return fmt.Errorf("no measurement in template `%s`", template)
	}

	return nil
}

func (c *Config) validateFilter(filter string) error {
	for _, p := range strings.Split(filter, ".") {
		if p == "" {
			return fmt.Errorf("filter contains blank section: %s", filter)
		}

		if strings.Contains(p, "*") && p != "*" {
			return fmt.Errorf("invalid filter wildcard section: %s", filter)
		}
	}
	return nil
}

func (c *Config) validateTag(keyValue string) error {
	parts := strings.Split(keyValue, "=")
	if len(parts) != 2 {
		return fmt.Errorf("invalid template tags: '%s'", keyValue)
	}

	if parts[0] == "" || parts[1] == "" {
		return fmt.Errorf("invalid template tags: %s'", keyValue)
	}

	return nil
}