// Package chain keeps the controller's chain on the bus alone (novox/hq ADR 0408, design 47): module, commit, build,
// published artifact or package, rollout and assignment are one chain, a bucket each of the bus's key-value store,
// each the only source of its kind, written by the controller that holds the lease by compare-and-set.
//
// **No key is removed.** A Backend has no delete and no purge (ADR 0408 §4): an assignment of a module taken off its
// node is kept, saying so. **A value is never cut** (§6): one over the largest the bus holds is refused, and the key
// stays as it was. **Each key keeps its earlier values** (§5), read back with History.
package chain

import (
	"encoding/json"
	"time"
)

// Ref names a build and the commit it was made from: one end of a change.
type Ref struct {
	Build  string `json:"build,omitempty"`
	Commit string `json:"commit,omitempty"`
}

// Package is a release a build published to the package registry.
type Package struct {
	Name    string `json:"name"`
	Version string `json:"version"`
}

// Published is what a build published: an artifact by its digest, or a package release by name and version.
type Published struct {
	Artifact string   `json:"artifact,omitempty"`
	Package  *Package `json:"package,omitempty"`
}

// Artifact is one thing a build made.
type Artifact struct {
	Name      string `json:"name"`
	Kind      string `json:"kind"`
	Reference string `json:"reference"`
}

// ReadRepository is a repository a build read source from besides the module's own.
type ReadRepository struct {
	Repository string   `json:"repository"`
	Ref        string   `json:"ref,omitempty"`
	Paths      []string `json:"paths,omitempty"`
	Own        bool     `json:"own,omitempty"`
}

// Source is the build source a build read in one repository.
type Source struct {
	Repository string   `json:"repository,omitempty"`
	Ref        string   `json:"ref,omitempty"`
	Paths      []string `json:"paths"`
}

// The states of a build record. A record in state asked is a request that no outcome has answered (issue 1091); one
// without a state is an outcome, and keeps the Request it was asked with.
const BuildAsked = "asked"

// The states of a request's Reask.
const (
	ReaskPending = "pending"
	ReaskClaimed = "claimed"
)

// Request is a build as it was asked for (novox/hq issue 325, ADR 0408 §1): kept in the build's own record under its id,
// first alone as state asked and then beside the outcome that answered it.
type Request struct {
	// Repository and Seat are the source as the mesh spells it; Path is the module's directory in it, Ref the branch or
	// commit asked, and Commit the commit that made the ask, where one did.
	Repository string `json:"repository,omitempty"`
	Seat       string `json:"seat,omitempty"`
	Path       string `json:"path,omitempty"`
	Ref        string `json:"ref,omitempty"`
	Commit     string `json:"commit,omitempty"`
	// For says who asked: merge, plan, build (a person), assign.
	For string `json:"for,omitempty"`
	// NotAsked is why the ask could not be handed over; OutcomeUnknown why an asker that handed it over stopped waiting.
	NotAsked       string    `json:"not-asked,omitempty"`
	OutcomeUnknown string    `json:"outcome-unknown,omitempty"`
	At             time.Time `json:"at,omitzero"`
	AtTerminal     bool      `json:"at-terminal,omitempty"`
	// Reask is, on a request the move found never handed over, "pending" until the controller asks it again, "claimed"
	// while it does, and the build id it was asked as once it has: published once, never twice (issue 981 note 7 Q5).
	Reask string `json:"reask,omitempty"`
}

// Build is one attempt, whichever way it went, kept under its id. It names its module, its repository and commit, its
// reuse key (novox/hq ADR 0350) and what it published (ADR 0408 §1).
type Build struct {
	ID         string          `json:"id"`
	State      string          `json:"state,omitempty"`
	Repository string          `json:"repository"`
	Ref        string          `json:"ref,omitempty"`
	Module     string          `json:"module,omitempty"`
	Commit     string          `json:"commit,omitempty"`
	On         string          `json:"on,omitempty"`
	Path       string          `json:"path,omitempty"`
	Manifest   json.RawMessage `json:"manifest,omitempty"`
	// ManifestDigest names the manifest in the manifests bucket (ManifestKey); a record that has it keeps no Manifest.
	ManifestDigest    string           `json:"manifest-digest,omitempty"`
	Against           []string         `json:"against,omitempty"`
	Mirrored          []string         `json:"mirrored,omitempty"`
	Read              []ReadRepository `json:"read,omitempty"`
	Sources           []Source         `json:"sources,omitempty"`
	SourceFingerprint string           `json:"source-fingerprint,omitempty"`
	Failed            string           `json:"failed,omitempty"`
	Made              []Artifact       `json:"made,omitempty"`
	Asked             time.Time        `json:"asked,omitzero"`
	At                time.Time        `json:"at,omitzero"`
	ReuseKey          string           `json:"reuse-key,omitempty"`
	Published         *Published       `json:"published,omitempty"`
	Request           *Request         `json:"request,omitempty"`
}

// Commit is one repository's commit a rollout carries.
type Commit struct {
	Repository string    `json:"repository"`
	Branch     string    `json:"branch,omitempty"`
	Commit     string    `json:"commit"`
	Merged     time.Time `json:"merged,omitzero"`
}

// Change is one assignment a rollout changed: the build and commit it ran before and the ones it runs after.
type Change struct {
	Node   string `json:"node"`
	Module string `json:"module"`
	Before Ref    `json:"before"`
	After  Ref    `json:"after"`
}

// Step is one tier sent to one machine.
type Step struct {
	Tier     int        `json:"tier"`
	Node     string     `json:"node"`
	Sent     *time.Time `json:"sent,omitempty"`
	Reported *time.Time `json:"reported,omitempty"`
}

// Links are the fields a rollout gains on the chain: the builds it carried, the machine steps it has taken and the
// assignments it changed, each with the build before and after. The controller's plan embeds them, so the plan's own
// fields and these are one value (ADR 0408 §1).
type Links struct {
	Builds  []string `json:"builds,omitempty"`
	Steps   []Step   `json:"steps,omitempty"`
	Changed []Change `json:"changed,omitempty"`
}

// HeldMerge is a merge a rollout holds: the columns the controller's table of batched merges had, kept in the record of the
// batch or walk that answers it (novox/hq ADR 0276, issue 1092). A merge no plan answers (Waiting) stays in the record
// that held it last. Placed is when it entered this record, so one found in two records after a crash between the two
// writes is read from the one it entered last.
type HeldMerge struct {
	Repository string          `json:"repository"`
	Branch     string          `json:"branch,omitempty"`
	Commit     string          `json:"commit"`
	Merged     time.Time       `json:"merged,omitzero"`
	Heard      time.Time       `json:"heard,omitzero"`
	Event      json.RawMessage `json:"event,omitempty"`
	Alone      bool            `json:"alone,omitempty"`
	Waiting    bool            `json:"waiting,omitempty"`
	Placed     time.Time       `json:"placed,omitzero"`
}

// Rollout is the controller's record of one batch's delivery, kept under the batch's id: the commit it fixed per
// repository, its tiers, the builds it carried and the assignments it changed (ADR 0408 §1). The controller's plan
// carries more (its modules, its times, its backups) beside these, under the same key.
type Rollout struct {
	ID      string     `json:"id"`
	State   string     `json:"state,omitempty"`
	Commits []Commit   `json:"commits,omitempty"`
	Tiers   [][]string `json:"tiers,omitempty"`
	Links
}

// Assignment is one module on one node, kept under `<node>.<module>`. The first five fields are the ones its readers
// have always read, with the names they have always had (novox/hq ADR 0408 §3); the rest name the chain: the build, the
// artifact (by digest) or the package it runs, its commit, the rollout that put it there and since when.
type Assignment struct {
	Node         string          `json:"node"`
	Module       string          `json:"module"`
	Assigned     time.Time       `json:"assigned,omitzero"`
	RequiredBy   string          `json:"required-by,omitempty"`
	Provisioning json.RawMessage `json:"provisioning,omitempty"`

	Build    string    `json:"build,omitempty"`
	Artifact string    `json:"artifact,omitempty"`
	Package  *Package  `json:"package,omitempty"`
	Commit   string    `json:"commit,omitempty"`
	Rollout  string    `json:"rollout,omitempty"`
	Since    time.Time `json:"since,omitzero"`

	// Ended is when the assignment ended (an unassignment): absent while it stands. **No key of the chain is removed**
	// (ADR 0408 §4), so an unassigned module keeps its key, saying so; every reader treats a value with Ended, or with a
	// State, as no assignment. State is StatePending while the key holds an assignment waiting for its build, or one that
	// was never made (issue 1094).
	Ended time.Time `json:"ended,omitzero"`
	State string    `json:"state,omitempty"`
	// Pending is the assignment's wait for its build (novox/hq ADR 0261), kept in the value of the key it waits for and, when
	// it is made, carried into the value that stands: the record of what became of the wait.
	Pending *Pending `json:"pending,omitempty"`

	// PulledIn marks a standing value of a module that is on the machine only because another requires it, or because a
	// send carried it: no time assigned, but a key all the same, so what the machine was sent of it is kept and read
	// (issue 1109). Never a state: every reader treats a non-empty state as no assignment, and would take it off the machine.
	PulledIn bool `json:"pulled-in,omitempty"`
	// SentUnknown is when a send by hand made what the machine runs unknown (a declaration sent with no builds known): the
	// commit is cleared with it. Absent normally; a send that names its builds clears it.
	SentUnknown time.Time `json:"sent-unknown,omitzero"`
}

// StatePending is the State of a value that holds no assignment but a pending one.
const StatePending = "pending"

// The states of a pending assignment (novox/hq ADR 0261).
const (
	PendingWaiting   = "waiting"
	PendingApplying  = "applying"
	PendingApplied   = "applied"
	PendingRefused   = "refused"
	PendingExpired   = "expired"
	PendingWithdrawn = "withdrawn"
)

// Pending is an assignment kept until its module is registered: the build it waits for, where that build is from, and the
// times of its claim and its end. Its id is p-<unix nanoseconds of Since>, unique for a key, which holds one at a time.
type Pending struct {
	ID           string     `json:"id"`
	State        string     `json:"state"`
	Build        string     `json:"build,omitempty"`
	Repository   string     `json:"repository,omitempty"`
	Path         string     `json:"path,omitempty"`
	Since        time.Time  `json:"since"`
	Note         string     `json:"note,omitempty"`
	Settled      *time.Time `json:"settled,omitempty"`
	Raised       *time.Time `json:"raised,omitempty"`
	Acknowledged *time.Time `json:"acknowledged,omitempty"`
	Cleared      *time.Time `json:"cleared,omitempty"`
	// Earlier are the waits of this key that ended unmade and were replaced by this one before their condition was answered
	// (taken back or cleared): each stays, with its own marks, so a replaced wait never leaves the operator without the
	// condition it raised or was to raise. Dropped once answered.
	Earlier []Pending `json:"earlier,omitempty"`
}

// Open says the assignment is still to be made.
func (p Pending) Open() bool { return p.State == PendingWaiting || p.State == PendingApplying }

// CanSettle says a pending assignment in state from may end in state to: a wait expires or is withdrawn, a claim becomes
// applied or refused, and nothing else.
func CanSettle(from, to string) bool {
	switch from {
	case PendingWaiting:
		return to == PendingExpired || to == PendingWithdrawn
	case PendingApplying:
		return to == PendingApplied || to == PendingRefused
	}
	return false
}

// CanMove says a pending assignment in state from may go to state to without ending: claimed, or released again.
func CanMove(from, to string) bool {
	return (from == PendingWaiting && to == PendingApplying) || (from == PendingApplying && to == PendingWaiting)
}

// Stands says the value is an assignment that holds: it has not ended and is not waiting in a state of its own.
func (a Assignment) Stands() bool { return a.Ended.IsZero() && a.State == "" }

// Key is an assignment's key.
func (a Assignment) Key() string { return a.Node + "." + a.Module }