package azurerm

import (
	"fmt"
	"net/url"
	"strings"
)

// ResourceID represents a parsed long-form Azure Resource Manager ID
// with the Subscription ID, Resource Group and the Provider as top-
// level fields, and other key-value pairs available via a map in the
// Path field.
type ResourceID struct {
	SubscriptionID string
	ResourceGroup  string
	Provider       string
	Path           map[string]string
}

// parseAzureResourceID converts a long-form Azure Resource Manager ID
// into a ResourceID. We make assumptions about the structure of URLs,
// which is obviously not good, but the best thing available given the
// SDK.
func parseAzureResourceID(id string) (*ResourceID, error) {
	idURL, err := url.ParseRequestURI(id)
	if err != nil {
		return nil, fmt.Errorf("Cannot parse Azure Id: %s", err)
	}

	path := idURL.Path

	path = strings.TrimSpace(path)
	if strings.HasPrefix(path, "/") {
		path = path[1:]
	}

	if strings.HasSuffix(path, "/") {
		path = path[:len(path)-1]
	}

	components := strings.Split(path, "/")

	// We should have an even number of key-value pairs.
	if len(components)%2 != 0 {
		return nil, fmt.Errorf("The number of path segments is not divisible by 2 in %q", path)
	}

	// Put the constituent key-value pairs into a map
	componentMap := make(map[string]string, len(components)/2)
	for current := 0; current < len(components); current += 2 {
		key := components[current]
		value := components[current+1]

		componentMap[key] = value
	}

	// Build up a ResourceID from the map
	idObj := &ResourceID{}
	idObj.Path = componentMap

	if subscription, ok := componentMap["subscriptions"]; ok {
		idObj.SubscriptionID = subscription
		delete(componentMap, "subscriptions")
	} else {
		return nil, fmt.Errorf("No subscription ID found in: %q", path)
	}

	if resourceGroup, ok := componentMap["resourceGroups"]; ok {
		idObj.ResourceGroup = resourceGroup
		delete(componentMap, "resourceGroups")
	} else {
		// Some Azure APIs are weird and provide things in lower case...
		// However it's not clear whether the casing of other elements in the URI
		// matter, so we explicitly look for that case here.
		if resourceGroup, ok := componentMap["resourcegroups"]; ok {
			idObj.ResourceGroup = resourceGroup
			delete(componentMap, "resourcegroups")
		} else {
			return nil, fmt.Errorf("No resource group name found in: %q", path)
		}
	}

	// It is OK not to have a provider in the case of a resource group
	if provider, ok := componentMap["providers"]; ok {
		idObj.Provider = provider
		delete(componentMap, "providers")
	}

	return idObj, nil
}