package dynamicparameters

import (
	"bytes"
	"context"
	_ "embed"
	"encoding/json"
	"fmt"
	"io"
	"strings"
	"text/template"
	"time"

	"github.com/google/uuid"
	"golang.org/x/xerrors"

	"cdr.dev/slog/v3"
	"github.com/coder/coder/v2/codersdk"
	"github.com/coder/coder/v2/cryptorand"
	"github.com/coder/coder/v2/scaletest/loadtestutil"
	"github.com/coder/quartz"
)

var ErrNoProvisionersMatched = xerrors.New("no provisioners matched")

//go:embed tf/main.tf
var templateContent string

func TemplateContent() (string, error) {
	randomString, err := cryptorand.String(8)
	if err != nil {
		return "", err
	}
	tmpl, err := template.New("workspace-template").Parse(templateContent)
	if err != nil {
		return "", err
	}
	var result strings.Builder
	err = tmpl.Execute(&result, map[string]string{
		"RandomString": randomString,
	})
	if err != nil {
		return "", err
	}
	return result.String(), nil
}

//go:embed tf/modules/two/main.tf
var moduleTwoMainTF string

// GetModuleFiles returns a map of module files to be used with ExtraFiles
func GetModuleFiles() map[string][]byte {
	// Create the modules.json that Terraform needs to see the module
	modulesJSON := struct {
		Modules []struct {
			Key    string `json:"Key"`
			Source string `json:"Source"`
			Dir    string `json:"Dir"`
		} `json:"Modules"`
	}{
		Modules: []struct {
			Key    string `json:"Key"`
			Source string `json:"Source"`
			Dir    string `json:"Dir"`
		}{
			{
				Key:    "",
				Source: "",
				Dir:    ".",
			},
			{
				Key:    "two",
				Source: "./modules/two",
				Dir:    "modules/two",
			},
		},
	}

	modulesJSONBytes, err := json.Marshal(modulesJSON)
	if err != nil {
		panic(err) // This should never happen with static data
	}

	return map[string][]byte{
		"modules/two/main.tf":             []byte(moduleTwoMainTF),
		".terraform/modules/modules.json": modulesJSONBytes,
	}
}

func TemplateTarData() ([]byte, error) {
	mainTF, err := TemplateContent()
	if err != nil {
		return nil, xerrors.Errorf("failed to generate main.tf: %w", err)
	}
	moduleFiles := GetModuleFiles()

	files := map[string][]byte{
		"main.tf": []byte(mainTF),
	}
	for k, v := range moduleFiles {
		files[k] = v
	}
	tarData, err := loadtestutil.CreateTarFromFiles(files)
	if err != nil {
		return nil, xerrors.Errorf("failed to create tarball: %w", err)
	}

	return tarData, nil
}

type Partition struct {
	TemplateVersion       codersdk.TemplateVersion
	ConcurrentEvaluations int
}

type SDKForDynamicParametersSetup interface {
	TemplateByName(ctx context.Context, orgID uuid.UUID, templateName string) (codersdk.Template, error)
	CreateTemplate(ctx context.Context, orgID uuid.UUID, createReq codersdk.CreateTemplateRequest) (codersdk.Template, error)
	CreateTemplateVersion(ctx context.Context, orgID uuid.UUID, createReq codersdk.CreateTemplateVersionRequest) (codersdk.TemplateVersion, error)
	Upload(ctx context.Context, contentType string, reader io.Reader) (codersdk.UploadResponse, error)
	TemplateVersion(ctx context.Context, versionID uuid.UUID) (codersdk.TemplateVersion, error)
}

// partitioner is an internal struct to hold context and arguments for partition setup
// and to provide methods for all sub-steps.
type partitioner struct {
	ctx             context.Context
	client          SDKForDynamicParametersSetup
	orgID           uuid.UUID
	templateName    string
	provisionerTags map[string]string
	numEvals        int64
	logger          slog.Logger

	// for testing
	clock quartz.Clock
}

func SetupPartitions(
	ctx context.Context, client SDKForDynamicParametersSetup,
	orgID uuid.UUID, templateName string, provisionerTags map[string]string,
	numEvals int64,
	logger slog.Logger,
) ([]Partition, error) {
	p := &partitioner{
		ctx:             ctx,
		client:          client,
		orgID:           orgID,
		templateName:    templateName,
		provisionerTags: provisionerTags,
		numEvals:        numEvals,
		logger:          logger,
		clock:           quartz.NewReal(),
	}
	return p.run()
}

func (p *partitioner) run() ([]Partition, error) {
	var (
		err         error
		coderError  *codersdk.Error
		templ       codersdk.Template
		tempVersion codersdk.TemplateVersion
	)
	templ, err = p.client.TemplateByName(p.ctx, p.orgID, p.templateName)
	if xerrors.As(err, &coderError) && coderError.StatusCode() == 404 {
		tempVersion, err = p.createTemplateVersion(uuid.Nil)
		if err != nil {
			return nil, xerrors.Errorf("failed to create template version: %w", err)
		}
		p.logger.Info(p.ctx, "created template version", slog.F("version_id", tempVersion.ID))
		createReq := codersdk.CreateTemplateRequest{
			Name:        p.templateName,
			DisplayName: "Scaletest Dynamic Parameters",
			Description: "`coder exp scaletest dynamic parameters test` template",
			VersionID:   tempVersion.ID,
		}
		templ, err = p.client.CreateTemplate(p.ctx, p.orgID, createReq)
		if err != nil {
			return nil, xerrors.Errorf("failed to create template: %w", err)
		}
		p.logger.Info(p.ctx, "created template", slog.F("template_id", templ.ID), slog.F("name", p.templateName))
	} else if err != nil {
		return nil, xerrors.Errorf("failed to get template: %w", err)
	}

	// Partition the number into a list decreasing by half each time
	evalParts := partitionEvaluations(int(p.numEvals))
	p.logger.Info(p.ctx, "partitioned evaluations", slog.F("num_evals", p.numEvals), slog.F("eval_parts", evalParts))

	// If tempVersion is not empty (i.e. we created it above), use it as the first version.
	partitions := make([]Partition, 0, len(evalParts))
	if tempVersion.ID != uuid.Nil {
		partitions = append(partitions, Partition{
			TemplateVersion:       tempVersion,
			ConcurrentEvaluations: evalParts[0],
		})
		evalParts = evalParts[1:]
	}

	for _, num := range evalParts {
		version, err := p.createTemplateVersion(templ.ID)
		if err != nil {
			return nil, xerrors.Errorf("failed to create template version: %w", err)
		}
		partitions = append(partitions, Partition{
			TemplateVersion:       version,
			ConcurrentEvaluations: num,
		})
		p.logger.Info(p.ctx, "created template version", slog.F("version_id", version.ID))
	}

	err = p.waitForTemplateVersionJobs(partitions)
	if err != nil {
		return nil, xerrors.Errorf("one or more template version jobs did not succeed: %w", err)
	}
	return partitions, nil
}

func (p *partitioner) createTemplateVersion(templateID uuid.UUID) (codersdk.TemplateVersion, error) {
	tarData, err := TemplateTarData()
	if err != nil {
		return codersdk.TemplateVersion{}, xerrors.Errorf("failed to create template tarball: %w", err)
	}

	// Upload tarball
	uploadResp, err := p.client.Upload(p.ctx, codersdk.ContentTypeTar, bytes.NewReader(tarData))
	if err != nil {
		return codersdk.TemplateVersion{}, xerrors.Errorf("failed to upload template tar: %w", err)
	}

	// Create template version
	versionReq := codersdk.CreateTemplateVersionRequest{
		TemplateID:      templateID,
		FileID:          uploadResp.ID,
		Message:         "Initial version for scaletest dynamic parameters",
		StorageMethod:   codersdk.ProvisionerStorageMethodFile,
		Provisioner:     codersdk.ProvisionerTypeTerraform,
		ProvisionerTags: p.provisionerTags,
	}
	version, err := p.client.CreateTemplateVersion(p.ctx, p.orgID, versionReq)
	if err != nil {
		return codersdk.TemplateVersion{}, xerrors.Errorf("failed to create template version: %w", err)
	}
	if version.MatchedProvisioners != nil && version.MatchedProvisioners.Count == 0 {
		return codersdk.TemplateVersion{}, ErrNoProvisionersMatched
	}
	return version, nil
}

func (p *partitioner) waitForTemplateVersionJobs(partitions []Partition) error {
	const pollInterval = 2 * time.Second
	done := xerrors.New("done")

	pending := make(map[uuid.UUID]int)
	for i, part := range partitions {
		pending[part.TemplateVersion.ID] = i
	}

	tkr := p.clock.TickerFunc(p.ctx, pollInterval, func() error {
		for versionID := range pending {
			version, err := p.client.TemplateVersion(p.ctx, versionID)
			if err != nil {
				return xerrors.Errorf("failed to fetch template version %s: %w", versionID, err)
			}
			status := version.Job.Status
			p.logger.Info(p.ctx, "polled template version job", slog.F("version_id", versionID), slog.F("status", status))
			switch status {
			case codersdk.ProvisionerJobSucceeded:
				delete(pending, versionID)
			case codersdk.ProvisionerJobPending, codersdk.ProvisionerJobRunning:
				continue
			default:
				return ProvisionerJobUnexpectedStatusError{
					TemplateVersionID: versionID,
					Status:            status,
					JobError:          version.Job.Error,
				}
			}
		}
		if len(pending) == 0 {
			return done
		}
		return nil
	}, "waitForTemplateVersionJobs")
	err := tkr.Wait()
	if xerrors.Is(err, done) {
		return nil
	}
	return err
}

func partitionEvaluations(total int) []int {
	var parts []int
	remaining := total
	for remaining > 0 {
		next := remaining / 2
		// round up
		if next*2 != remaining {
			next++
		}
		if next > remaining {
			next = remaining
		}
		parts = append(parts, next)
		remaining -= next
	}
	return parts
}

type ProvisionerJobUnexpectedStatusError struct {
	TemplateVersionID uuid.UUID
	Status            codersdk.ProvisionerJobStatus
	JobError          string
}

func (e ProvisionerJobUnexpectedStatusError) Error() string {
	return fmt.Sprintf("template version %s job in unexpected status %q, error '%s'", e.TemplateVersionID, e.Status, e.JobError)
}