package cloudbuilder

import (
	"bytes"
	_ "embed"
	"errors"
	"fmt"
	"net/smtp"
	"os"
	"path"
	"regexp"
	"strconv"
	"strings"
	"text/template"
	"time"

	"github.com/rs/zerolog/log"

	"git.csclub.uwaterloo.ca/cloud/cloudbuild/pkg/cloudstack"
	"git.csclub.uwaterloo.ca/cloud/cloudbuild/pkg/config"
	"git.csclub.uwaterloo.ca/cloud/cloudbuild/pkg/distros"
)

//go:embed email-message.txt
var emailMessageTemplate string

type CloudBuilder struct {
	cfg    *config.Config
	client *cloudstack.CloudstackClient
}

func New(cfg *config.Config) *CloudBuilder {
	return &CloudBuilder{
		cfg:    cfg,
		client: cloudstack.New(cfg),
	}
}

func (c *CloudBuilder) moveTemplateToUploadArea(templatePath string) (newPath string, err error) {
	newPath = path.Join(c.cfg.UploadDirectory, path.Base(templatePath))
	log.Debug().Msg(fmt.Sprintf("Moving %s to %s", templatePath, newPath))
	err = os.Rename(templatePath, newPath)
	return
}

func (c *CloudBuilder) UploadTemplate(
	templatePath string, templateName string, osDescription string,
) (template *cloudstack.Template, err error) {
	templatePath, err = c.moveTemplateToUploadArea(templatePath)
	if err != nil {
		return
	}
	osTypeId, err := c.client.GetOsTypeId(osDescription)
	if err != nil {
		return
	}
	uploadUrl := strings.TrimRight(c.cfg.UploadBaseUrl, "/") + "/" + path.Base(templatePath)
	log.Debug().Msg(fmt.Sprintf("Uploading new template from %s", uploadUrl))
	template, err = c.client.RegisterTemplate(templateName, uploadUrl, osTypeId)
	if err != nil {
		return
	}
	const pollInterval = 5 * time.Second
	// Due to clock drift, we may end up waiting a bit longer than this
	const maxTimeToWait = 5 * time.Minute
	var timeWaited time.Duration = 0
	for !template.IsReady {
		// TODO: make sure that DownloadDetails[0] exists
		log.Debug().
			Str("templateName", template.Name).
			Str("status", template.Status).
			Str("downloadPercent", template.DownloadDetails[0].DownloadPercent).
			Str("downloadState", template.DownloadDetails[0].DownloadState).
			Msg("Template is not ready yet...")
		time.Sleep(pollInterval)
		timeWaited += pollInterval
		if timeWaited >= maxTimeToWait {
			err = errors.New("Timed out waiting for template to be ready")
			return
		}
		template, err = c.client.GetTemplate(template.Id)
		if err != nil {
			return
		}
	}
	log.Debug().Msg("Deleting " + templatePath)
	err = os.Remove(templatePath)
	return
}

func (c *CloudBuilder) CreateVM(
	name string, templateID string,
) (virtualMachine *cloudstack.VirtualMachine, err error) {
	vmID, err := c.client.DeployVirtualMachine(name, templateID)
	if err != nil {
		return
	}
	virtualMachine, err = c.client.GetVirtualMachine(vmID)
	if err != nil {
		return
	}
	const pollInterval = 20 * time.Second
	// Due to clock drift, we may end up waiting a bit longer than this
	const maxTimeToWait = 30 * time.Minute
	var timeWaited time.Duration = 0
	log.Debug().Str("templateID", templateID).Msg("Creating new VM")
	for virtualMachine.State != "Running" {
		log.Debug().
			Str("name", name).
			Str("id", virtualMachine.Id).
			Str("state", virtualMachine.State).
			Msg("VM is not ready yet...")
		time.Sleep(pollInterval)
		timeWaited += pollInterval
		if timeWaited >= maxTimeToWait {
			err = errors.New("Timed out waiting for VM to be ready")
			return
		}
		virtualMachine, err = c.client.GetVirtualMachine(vmID)
		if err != nil {
			return
		}
	}
	log.Debug().Msg("VM successfully created")
	return
}

type DistroInfo struct {
	name          string
	manager       distros.ITemplateManager
	osDescription string
	user          string
}

type TemplateVersionInfo struct {
	TemplateId string
	Version    string
}

func (c *CloudBuilder) getExistingTemplateVersions() map[string]TemplateVersionInfo {
	templatePattern := regexp.MustCompile("^CSC (?P<distro>[A-Za-z][A-Za-z ]+[A-Za-z]) (?P<version>\\d+(\\.\\d+)?)$")
	mostRecentVersions := make(map[string]TemplateVersionInfo)
	templates := c.client.ListTemplates()
	for _, template := range templates {
		submatches := templatePattern.FindStringSubmatch(template.Name)
		if submatches == nil {
			log.Debug().Msg(fmt.Sprintf("Template '%s' did not match pattern, skipping", template.Name))
			continue
		}
		distro := submatches[1]
		version := submatches[2]
		log.Debug().Str("distro", distro).Str("version", version).Msg("Found template")
		otherVersion, ok := mostRecentVersions[distro]
		if !ok || version > otherVersion.Version {
			mostRecentVersions[distro] = TemplateVersionInfo{
				TemplateId: template.Id,
				Version:    version,
			}
		}
	}
	return mostRecentVersions
}

func (c *CloudBuilder) sendEmailNotification(templateName string) (err error) {
	tmpl := template.Must(template.New("email-message").Parse(emailMessageTemplate))
	data := map[string]interface{}{
		"cfg":          c.cfg,
		"date":         time.Now().Format(time.RFC1123Z),
		"templateName": templateName,
	}
	var buf bytes.Buffer
	if err = tmpl.Execute(&buf, data); err != nil {
		return
	}
	// The lines of the body need to be CRLF terminated
	// See https://pkg.go.dev/net/smtp#SendMail
	// Make sure that email-message.txt uses Unix-style LF endings
	msg := bytes.ReplaceAll(buf.Bytes(), []byte("\n"), []byte("\r\n"))
	log.Debug().
		Str("to", c.cfg.EmailRecipient).
		Msg("sending email notification")
	return smtp.SendMail(
		c.cfg.EmailServer,
		nil, /* auth */
		c.cfg.EmailSender,
		[]string{c.cfg.EmailRecipient},
		msg,
	)
}

func (c *CloudBuilder) createNewTemplate(
	newVersion, codename string, distroInfo *DistroInfo,
) (template *cloudstack.Template, err error) {
	distroManager := distroInfo.manager
	templatePath, err := distroManager.DownloadTemplate(newVersion, codename)
	if err != nil {
		return
	}
	if err = distroManager.ModifyTemplate(templatePath); err != nil {
		return
	}
	templateName := fmt.Sprintf("CSC %s %s", distroInfo.name, newVersion)
	template, err = c.UploadTemplate(templatePath, templateName, distroInfo.osDescription)
	return
}

func (c *CloudBuilder) destroyVirtualMachine(vmID string) error {
	log.Info().Str("id", vmID).Msg("Deleting VM")
	deletionJobID, err := c.client.DestroyVirtualMachine(vmID)
	if err != nil {
		return err
	}
	return c.client.WaitForJobToComplete(deletionJobID)
}

func (c *CloudBuilder) versionStringCompare(version1, version2 string) int {
	f1, err := strconv.ParseFloat(version1, 32)
	if err != nil {
		panic(err)
	}
	f2, err := strconv.ParseFloat(version2, 32)
	if err != nil {
		panic(err)
	}
	if f1 < f2 {
		return -1
	} else if f1 > f2 {
		return 1
	}
	return 0
}

func (c *CloudBuilder) Start() (err error) {
	distrosInfo := map[string]DistroInfo{
		"debian": DistroInfo{
			name:    "Debian",
			manager: distros.NewDebianTemplateManager(c.cfg),
			// This is the latest version available in CloudStack 4.16;
			// using a custom OS type caused issues with the ethernet
			// interface not being detected
			osDescription: "Debian GNU/Linux 11 (64-bit)",
			user:          "debian",
		},
		"ubuntu": DistroInfo{
			name:          "Ubuntu",
			manager:       distros.NewUbuntuTemplateManager(c.cfg),
			osDescription: "Other Ubuntu (64-bit)",
			user:          "ubuntu",
		},
		"fedora": DistroInfo{
			name:          "Fedora",
			manager:       distros.NewFedoraTemplateManager(c.cfg),
			osDescription: "Fedora Linux (64 bit)",
			user:          "fedora",
		},
		"almalinux": DistroInfo{
			name:          "AlmaLinux",
			manager:       distros.NewAlmaLinuxTemplateManager(c.cfg),
			osDescription: "Other CentOS (64-bit)",
			user:          "almalinux",
		},
	}
	existingTemplates := c.getExistingTemplateVersions()
	newVersions := make(map[string]string)
	for _, distroLower := range c.cfg.DistrosToCheck {
		distroInfo, ok := distrosInfo[distroLower]
		if !ok {
			return errors.New("Distro not found: " + distroLower)
		}
		distro := distroInfo.name
		distroManager := distroInfo.manager
		var newVersion, codename string
		newVersion, codename, err = distroManager.GetLatestVersion()
		if err != nil {
			return
		}
		log.Debug().Str("newVersion", newVersion).Str("codename", codename).Msg(distro)

		curTemplate, ok := existingTemplates[distro]
		curVersion := curTemplate.Version
		if ok && c.versionStringCompare(newVersion, curVersion) <= 0 {
			log.Debug().
				Str("distro", distro).
				Str("version", curVersion).
				Msg("Existing version is up to date, skipping")
			continue
		}

		newVersions[distro] = newVersion
		log.Info().
			Str("distro", distroLower).
			Msg("Template is nonexistent or out of date, creating a new one")

		var template *cloudstack.Template
		template, err = c.createNewTemplate(newVersion, codename, &distroInfo)
		if err != nil {
			return
		}

		// Create a VM using the new template
		vmName := strings.Join([]string{
			strings.ReplaceAll(distroLower, " ", "-"),
			strings.ReplaceAll(newVersion, ".", "-"),
			"test",
		}, "-")
		var vm *cloudstack.VirtualMachine
		vm, err = c.CreateVM(vmName, template.Id)
		if err != nil {
			return
		}

		// Make sure that everything is working properly in the VM
		verifier := NewVMVerifier(c.cfg, distroInfo.user, vm.Nic[0].IpAddress, vmName, distroInfo.manager)
		if err = verifier.Verify(); err != nil {
			return
		}

		// Since we don't need the VM anymore, delete it
		if err = c.destroyVirtualMachine(vm.Id); err != nil {
			return
		}
		vm = nil

		// When we originally created the template, it wasn't public,
		// so make it public now
		if err = c.client.MakeTemplatePublicAndFeatured(template.Id); err != nil {
			return
		}

		if err = c.sendEmailNotification(template.Name); err != nil {
			return
		}
	}
	if c.cfg.DeleteOldTemplates {
		if err = c.DeleteOldTemplates(existingTemplates, newVersions); err != nil {
			return
		}
	}
	return
}