// Package proxmox implements the provider contract on a Proxmox VE cluster
// through its REST API: VMs are full clones of prepared templates, seeded
// with a NoCloud ISO uploaded to a storage and addressed through the guest
// agent. The design is in docs/proxmox-provider-spec.md.
package proxmox

import (
	"context"
	"fmt"
	"os"
	"time"

	"github.com/go-logr/logr"
	logf "sigs.k8s.io/controller-runtime/pkg/log"

	"gitea.home.hrajfrisbee.cz/kacerr/egress-proxies-operator/internal/provider"
	"gitea.home.hrajfrisbee.cz/kacerr/egress-proxies-operator/internal/provider/keyedlock"
)

const (
	defaultVMIDMin               = 100000
	defaultVMIDMax               = 199999
	defaultRequestTimeoutSeconds = 30
)

// budgets bounds every wait of the provider (spec entry 18); tests shrink
// them.
type budgets struct {
	clone      time.Duration // the clone task, and waiting for a VM's lock
	upload     time.Duration
	resize     time.Duration
	start      time.Duration
	stop       time.Duration
	destroy    time.Duration
	seedDelete time.Duration
	running    time.Duration // from the start task's end to status running
	poll       time.Duration // task and status poll interval
}

func defaultBudgets() budgets {
	return budgets{
		clone:      10 * time.Minute,
		upload:     2 * time.Minute,
		resize:     2 * time.Minute,
		start:      2 * time.Minute,
		stop:       2 * time.Minute,
		destroy:    5 * time.Minute,
		seedDelete: time.Minute,
		running:    60 * time.Second,
		poll:       time.Second,
	}
}

// Provider is one configured proxmox entry: one cluster reached through one
// API URL with one token.
type Provider struct {
	name    string
	cfg     provider.ProxmoxConfig
	api     api
	now     func() time.Time
	budgets budgets

	// nameLocks serialises Create and Delete per instance name (spec entry
	// 19), so the reconciler's Delete and GC's Delete never race on stop and
	// destroy, and a Delete cannot interleave with a Create's steps.
	nameLocks *keyedlock.Locks
}

var _ provider.Provider = (*Provider)(nil)

// New builds a Provider from pc.Proxmox. It never makes a request: the token
// file is only checked for existence, and a missing one is a warning, not an
// error, because the Secret mount is optional and may land later.
func New(ctx context.Context, pc provider.ProviderConfig) (provider.Provider, error) {
	cfg := provider.ProxmoxConfig{}
	if pc.Proxmox != nil {
		cfg = *pc.Proxmox
	}
	client, err := newHTTPAPI(withDefaults(cfg))
	if err != nil {
		return nil, fmt.Errorf("proxmox provider %s: %w", pc.Name, err)
	}
	p := newProvider(pc.Name, cfg, observe(client, pc.Name))
	log := p.logger(ctx)
	if _, err := os.Stat(p.cfg.TokenFile); err != nil {
		log.Info("WARNING: token file is not readable; every call fails until it is", "path", p.cfg.TokenFile, "reason", err.Error())
	}
	if p.cfg.InsecureSkipTLSVerify {
		log.Info("WARNING: insecureSkipTLSVerify is set; the API's certificate is not verified")
	}
	return p, nil
}

// newProvider is the constructor tests use, with an in-memory api.
func newProvider(name string, cfg provider.ProxmoxConfig, a api) *Provider {
	return &Provider{
		name:      name,
		cfg:       withDefaults(cfg),
		api:       a,
		now:       time.Now,
		budgets:   defaultBudgets(),
		nameLocks: keyedlock.New(),
	}
}

// withDefaults returns cfg with every optional field filled in, so the rest
// of the package never re-checks for an empty value. Slices, maps and
// pointers are copied, not shared with the caller.
func withDefaults(cfg provider.ProxmoxConfig) provider.ProxmoxConfig {
	cfg.Nodes = append([]string(nil), cfg.Nodes...)
	if cfg.VMIDRange == nil {
		cfg.VMIDRange = &provider.ProxmoxVMIDRange{Min: defaultVMIDMin, Max: defaultVMIDMax}
	} else {
		r := *cfg.VMIDRange
		cfg.VMIDRange = &r
	}
	if cfg.RequestTimeoutSeconds == 0 {
		cfg.RequestTimeoutSeconds = defaultRequestTimeoutSeconds
	}
	install := true
	if cfg.InstallGuestAgent != nil {
		install = *cfg.InstallGuestAgent
	}
	cfg.InstallGuestAgent = &install
	templates := make(map[string]provider.ProxmoxTemplate, len(cfg.Templates))
	for k, v := range cfg.Templates {
		templates[k] = v
	}
	cfg.Templates = templates
	machineTypes := make(map[string]provider.ProxmoxMachineType, len(cfg.MachineTypes))
	for k, v := range cfg.MachineTypes {
		machineTypes[k] = v
	}
	cfg.MachineTypes = machineTypes
	return cfg
}

func (p *Provider) logger(ctx context.Context) logr.Logger {
	return logf.FromContext(ctx).WithName("proxmox").WithValues("provider", p.name)
}

// node resolves placement.zone to a configured node. An empty zone is
// allowed only when exactly one node is configured.
func (p *Provider) node(zone string) (string, error) {
	if zone == "" {
		if len(p.cfg.Nodes) == 1 {
			return p.cfg.Nodes[0], nil
		}
		return "", permanentf("placement.zone is required when proxmox.nodes lists more than one node")
	}
	for _, n := range p.cfg.Nodes {
		if n == zone {
			return n, nil
		}
	}
	return "", permanentf("placement.zone %q is not in proxmox.nodes", zone)
}

// wrapErr is the single exit for errors: it classifies err and wraps it with
// the configured provider name, op and id.
func (p *Provider) wrapErr(op, id string, err error) error {
	return provider.Wrap(classify(op, err), op, p.name, id, err)
}

// lockName takes the per-name lock of spec entry 19, or gives up with ctx,
// so a caller whose ctx ends while another caller's Create waits on a clone
// returns promptly.
func (p *Provider) lockName(ctx context.Context, name string) (func(), error) {
	release, err := p.nameLocks.Acquire(ctx, name)
	if err != nil {
		return nil, fmt.Errorf("%w: waiting for the lock on %s: %w", provider.ErrTransient, name, err)
	}
	return release, nil
}

// The four contract methods are stubs until the phases that implement them
// (Get and ListByTag in Phase 5, Create in 6, Delete in 7). Each answers
// Transient, so a Proxy on this provider retries rather than latching.

func (p *Provider) Create(_ context.Context, req provider.CreateRequest) (string, error) {
	return "", p.wrapErr("create", "", transientf("proxmox Create is not implemented yet (request %s)", req.Name))
}

func (p *Provider) Get(_ context.Context, id string) (*provider.Instance, error) {
	return nil, p.wrapErr("get", id, transientf("proxmox Get is not implemented yet"))
}

func (p *Provider) Delete(_ context.Context, id string) error {
	return p.wrapErr("delete", id, transientf("proxmox Delete is not implemented yet"))
}

func (p *Provider) ListByTag(_ context.Context) ([]provider.Instance, error) {
	return nil, p.wrapErr("list", "", transientf("proxmox ListByTag is not implemented yet"))
}