package inventory

import (
	"fmt"
	"sort"
	"time"
)

// A machine has applied a send of a provisioned module only once its files are placed (novox/hq ADR 0362, design
// 57 P6, issue 672): for a module the send handed to the provisioner (SentDeclaration.Provisioned), the machine's
// own report that it applied the send is half of it, and its provisioner client's `prov.applied` for the build's
// templates the other half.
//
//   - both reported, applied: the send is applied, at the later of the two (ADR 0362 §5: delivery time runs to it);
//   - the client reported it failed on that build: a failed apply, named with its reason (§3);
//   - the client has not reported it applied on that build (not yet, waiting for a value, an older build): not yet
//     applied, and once ApplySilentAfter has passed since the send the walk names the machine silent (§4);
//   - a send that handed nothing: the machine's own report alone, as before.

// ProvReport is a provisioner client's newest report of one module on its machine, as `prov.applied` says it
// (mesh-catalog mesh-provisioner-client Report): applied, waiting, failed with the reason, or removed; the digest
// of the templates it filled from; and when it said it.
type ProvReport struct {
	Node      string    `json:"node"`
	Module    string    `json:"module"`
	Status    string    `json:"status"`
	Reason    string    `json:"reason,omitempty"`
	WaitsFor  []string  `json:"waits-for,omitempty"`
	Templates string    `json:"templates,omitempty"`
	At        time.Time `json:"at"`
}

// The words a client's report says.
const (
	ProvApplied = "applied"
	ProvWaiting = "waiting"
	ProvFailed  = "failed"
	ProvRemoved = "removed"
)

// ProvLookup answers a client's newest report of a module on a machine; false when it has said nothing of it.
type ProvLookup func(node, module string) (ProvReport, bool)

// OutcomeProvisioningFailed begins the outcome of a send whose module's files the provisioner failed to place.
const OutcomeProvisioningFailed = "provisioning failed"

// ProvisionedSend is a machine's report of a send, with its provisioner client's reports of every module the send
// handed to it: what a walk counts as that machine's report. engine and reported are the machine's own report and
// whether it said one. A failed client report is the send's outcome, whatever the machine said; none, or one not
// yet applied on the build sent, leaves the send unreported.
func ProvisionedSend(node string, send SentDeclaration, engine AppliedReport, reported bool, prov ProvLookup) (AppliedReport, bool) {
	if len(send.Provisioned) == 0 {
		return engine, reported
	}
	// The machine's own failure, or its wait for a busy container, is its report whatever the client says.
	if reported && (engine.Outcome != OutcomeApplied || engine.Waiting) {
		return engine, true
	}
	modules := make([]string, 0, len(send.Provisioned))
	for m := range send.Provisioned {
		modules = append(modules, m)
	}
	sort.Strings(modules)
	at, placed := engine.At, true
	for _, m := range modules {
		r, said := ProvReport{}, false
		if prov != nil {
			r, said = prov(node, m)
		}
		switch {
		case said && r.Status == ProvFailed && aboutTheSend(r, send, send.Provisioned[m]):
			return AppliedReport{At: r.At, Outcome: fmt.Sprintf("%s (%s: %s)", OutcomeProvisioningFailed, m,
				orNoReason(r.Reason))}, true
		case said && r.Status == ProvApplied && r.Templates == send.Provisioned[m]:
			if r.At.After(at) {
				at = r.At
			}
		default:
			placed = false
		}
	}
	if !reported || !placed {
		return AppliedReport{}, false
	}
	engine.At = at
	return engine, true
}

// Only is the send narrowed to what it handed to the provisioner for the named modules: a delivery waits on the
// modules it carries, never on another module the same machine's declaration hands (ADR 0362 §1-2, issue 840).
// A send handing nothing is returned as it is.
func (s SentDeclaration) Only(modules ...string) SentDeclaration {
	if len(s.Provisioned) == 0 {
		return s
	}
	kept := map[string]string{}
	for _, m := range modules {
		if d, ok := s.Provisioned[m]; ok {
			kept[m] = d
		}
	}
	s.Provisioned = kept
	return s
}

// aboutTheSend says a client's failure is about what the send handed: on the build's templates, or, said before it
// had any to name (its templates could not be fetched), no earlier than the send.
func aboutTheSend(r ProvReport, send SentDeclaration, digest string) bool {
	if r.Templates != "" {
		return r.Templates == digest
	}
	return send.At.IsZero() || !r.At.Before(send.At)
}

func orNoReason(s string) string {
	if s == "" {
		return "no reason given"
	}
	return s
}