package inventory

import (
	"context"
	"errors"
	"path"
	"strings"
	"time"

	"github.com/jackc/pgx/v5"
)

// What the controller asked to be built, and the assignments waiting for it (novox/hq issue 325, ADR 0261).
//
// A build's outcome was kept, and its asking was not: between a merge asking for a new module and the
// outcome registering it, the mesh had no record that anything was coming, and `assign` answered "no module
// of that name" for a module minutes from existing. Kept here, a build request lets `assign` say which case
// it is in, and an assignment made while the build runs is kept until the build registers the module.

// KeptFor is how long a build request, and an ended pending assignment, is kept.
const KeptFor = 30 * 24 * time.Hour

// BuildRequest is one build the controller asked for.
type BuildRequest struct {
	// ID is the build's id, as its outcome will carry it; for a merge whose ask could not be made, an id
	// of the controller's making that no build carries.
	ID string
	// Repository and Seat are the source as the mesh spells it (novox/hq ADR 0111): a path on the seat's
	// holder, or a URL with no seat. Path is the module's directory in it, Ref the branch or commit asked.
	Repository, Seat, Path, Ref string
	// Commit is the commit that made the ask, where one did: a merge's.
	Commit string
	// For says who asked: "merge", "plan", "build" (a person), "assign".
	For string
	// NotAsked is why the ask could not be handed over; empty when it was.
	NotAsked string
	// OutcomeUnknown is why an asker that handed the build over stopped waiting for it: asked, outcome
	// unknown. Read as in flight until its outcome or its bound.
	OutcomeUnknown string
	At             time.Time
	// AtTerminal says the request was asked at the controller's terminal, never through a verb (novox/hq ADR
	// 0266): what lets its outcome register a module from a repository the catalogue does not build it from.
	AtTerminal bool
}

// Name is the module this request is expected to register, read from its directory: the last element of
// its path, or of its repository for a module at the repository's root. A guess until the build says, and
// the one a person reads too: `modules/sensors` is sensors.
func (a BuildRequest) Name() string {
	if p := strings.Trim(a.Path, "/"); p != "" && p != "." {
		return path.Base(p)
	}
	return strings.TrimSuffix(path.Base(strings.TrimRight(a.Repository, "/")), ".git")
}

// RequestOutcome is a build request beside what came of it, where anything did.
type RequestOutcome struct {
	BuildRequest
	// Heard is whether an outcome of this id was taken in; Failed is its builder's words when it failed,
	// Module what the build said it built, HeardAt when it was taken in.
	Heard   bool
	Failed  string
	Module  string
	HeardAt time.Time
}

// RecordBuildRequest keeps one build request, once it is asked. Idempotent on the id. Requests older than
// KeptFor are deleted in the same act.
func (i *Inventory) RecordBuildRequest(ctx context.Context, a BuildRequest) error {
	at := a.At
	if at.IsZero() {
		at = time.Now().UTC()
	}
	var notAsked *string
	if a.NotAsked != "" {
		notAsked = &a.NotAsked
	}
	if _, err := i.store.Pool().Exec(ctx,
		`insert into build_request (id, repository, seat, source_path, ref, commit_hash, asked_for, not_asked, asked_at,
		                            at_terminal)
		 values ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
		 on conflict (id) do nothing`,
		a.ID, a.Repository, a.Seat, strings.Trim(a.Path, "/"), a.Ref, a.Commit, a.For, notAsked, at,
		a.AtTerminal); err != nil {
		return err
	}
	_, err := i.store.Pool().Exec(ctx, `delete from build_request where asked_at < $1`, time.Now().Add(-KeptFor))
	return err
}

// BuildRequestByID is the build request kept under this id, and whether one was kept.
func (i *Inventory) BuildRequestByID(ctx context.Context, id string) (BuildRequest, bool, error) {
	var a BuildRequest
	err := i.store.Pool().QueryRow(ctx,
		`select id, repository, seat, source_path, ref, commit_hash, asked_for, at_terminal, asked_at
		   from build_request where id = $1`, id).Scan(&a.ID, &a.Repository, &a.Seat, &a.Path, &a.Ref, &a.Commit,
		&a.For, &a.AtTerminal, &a.At)
	if errors.Is(err, pgx.ErrNoRows) {
		return BuildRequest{}, false, nil
	}
	return a, err == nil, err
}

// MarkNotAsked says a kept build request was never handed over: the words are kept, unless its outcome was
// heard first.
func (i *Inventory) MarkNotAsked(ctx context.Context, id, why string) error {
	_, err := i.store.Pool().Exec(ctx,
		`update build_request set not_asked = $2
		  where id = $1 and not exists (select 1 from build where build.id = $1)`, id, why)
	return err
}

// MarkOutcomeUnknown says the asker of a build it handed over stopped waiting for it: asked, outcome unknown.
// The build may still run; its outcome, when heard, is the last word.
func (i *Inventory) MarkOutcomeUnknown(ctx context.Context, id, why string) error {
	_, err := i.store.Pool().Exec(ctx,
		`update build_request set outcome_unknown = $2
		  where id = $1 and not exists (select 1 from build where build.id = $1)`, id, why)
	return err
}

// RequestsNamed is every build request kept whose directory names the module, or whose build said it built
// it, newest first, each with its outcome.
func (i *Inventory) RequestsNamed(ctx context.Context, name string) ([]RequestOutcome, error) {
	all, err := i.requests(ctx)
	if err != nil {
		return nil, err
	}
	var out []RequestOutcome
	for _, a := range all {
		if a.Name() == name || a.Module == name {
			out = append(out, a)
		}
	}
	return out, nil
}

// RequestedNames is the name of every module a kept build request is expected to register: what `assign`
// offers as a closest name beside the modules registered.
func (i *Inventory) RequestedNames(ctx context.Context) ([]string, error) {
	all, err := i.requests(ctx)
	if err != nil {
		return nil, err
	}
	seen := map[string]bool{}
	var out []string
	for _, a := range all {
		if n := a.Name(); n != "" && !seen[n] {
			seen[n] = true
			out = append(out, n)
		}
	}
	return out, nil
}

func (i *Inventory) requests(ctx context.Context) ([]RequestOutcome, error) {
	rows, err := i.store.Pool().Query(ctx,
		`select a.id, a.repository, a.seat, a.source_path, a.ref, a.commit_hash, a.asked_for,
		        coalesce(a.not_asked, ''), coalesce(a.outcome_unknown, ''), a.asked_at,
		        b.id is not null, coalesce(b.failed, ''), coalesce(b.module, ''), coalesce(b.at, a.asked_at)
		   from build_request a left join build b on b.id = a.id
		  order by a.asked_at desc, a.id desc`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []RequestOutcome
	for rows.Next() {
		var a RequestOutcome
		if err := rows.Scan(&a.ID, &a.Repository, &a.Seat, &a.Path, &a.Ref, &a.Commit, &a.For, &a.NotAsked,
			&a.OutcomeUnknown, &a.At, &a.Heard, &a.Failed, &a.Module, &a.HeardAt); err != nil {
			return nil, err
		}
		out = append(out, a)
	}
	return out, rows.Err()
}

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

// PendingAssignment is an assignment kept until its module is registered (ADR 0261).
type PendingAssignment struct {
	ID     int64
	Node   string
	Module string
	// Build is the build it waits for; Repository and Path where that build is from.
	Build, Repository, Path string
	Since                   time.Time
	State                   string
	// Note is what ended it, in the words said when it ended.
	Note    string
	Settled *time.Time
	// Raised is when an expiry or refusal was raised as a condition; Acknowledged when a person took it
	// back; Cleared when its condition was cleared.
	Raised, Acknowledged, Cleared *time.Time
}

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

// ErrAlreadyPending is a second pending assignment of one module to one machine.
var ErrAlreadyPending = errors.New("that assignment is already waiting for its build")

const pendingColumns = `p.id, n.name, p.module, p.build_id, p.repository, p.source_path, p.since, p.state, p.note,
	p.settled_at, p.raised_at, p.acknowledged_at, p.cleared_at`

func scanPending(rows pgx.Rows) ([]PendingAssignment, error) {
	defer rows.Close()
	var out []PendingAssignment
	for rows.Next() {
		var p PendingAssignment
		if err := rows.Scan(&p.ID, &p.Node, &p.Module, &p.Build, &p.Repository, &p.Path, &p.Since, &p.State,
			&p.Note, &p.Settled, &p.Raised, &p.Acknowledged, &p.Cleared); err != nil {
			return nil, err
		}
		out = append(out, p)
	}
	return out, rows.Err()
}

// RecordPending keeps an assignment until its module is registered. One is open per machine and module.
func (i *Inventory) RecordPending(ctx context.Context, p PendingAssignment) (PendingAssignment, error) {
	node, err := i.NodeByName(ctx, p.Node)
	if err != nil {
		return PendingAssignment{}, err
	}
	err = i.store.Pool().QueryRow(ctx,
		`insert into pending_assignment (node, module, build_id, repository, source_path)
		 values ($1, $2, $3, $4, $5)
		 on conflict (node, module) where state in ('waiting', 'applying') do nothing
		 returning id, since`,
		node.ID, p.Module, p.Build, p.Repository, strings.Trim(p.Path, "/")).Scan(&p.ID, &p.Since)
	if errors.Is(err, pgx.ErrNoRows) {
		return PendingAssignment{}, ErrAlreadyPending
	}
	if err != nil {
		return PendingAssignment{}, err
	}
	p.State = PendingWaiting
	return p, nil
}

// RepointPending makes a waiting pending assignment wait for another build. False when it no longer waits.
func (i *Inventory) RepointPending(ctx context.Context, id int64, build, repository, sourcePath string) (bool, error) {
	tag, err := i.store.Pool().Exec(ctx,
		`update pending_assignment set build_id = $2, repository = $3, source_path = $4
		  where id = $1 and state = 'waiting'`, id, build, repository, strings.Trim(sourcePath, "/"))
	if err != nil {
		return false, err
	}
	return tag.RowsAffected() == 1, nil
}

// Pending is every pending assignment still waiting, oldest first, when endedSince is zero. Otherwise it is
// every open one and every one ended since then.
func (i *Inventory) Pending(ctx context.Context, endedSince time.Time) ([]PendingAssignment, error) {
	if endedSince.IsZero() {
		rows, err := i.store.Pool().Query(ctx, `select `+pendingColumns+`
			from pending_assignment p join node n on n.id = p.node
			where p.state = 'waiting' order by p.since, p.id`)
		if err != nil {
			return nil, err
		}
		return scanPending(rows)
	}
	rows, err := i.store.Pool().Query(ctx, `select `+pendingColumns+`
		from pending_assignment p join node n on n.id = p.node
		where p.state in ('waiting', 'applying') or p.settled_at >= $1
		order by p.since, p.id`, endedSince)
	if err != nil {
		return nil, err
	}
	return scanPending(rows)
}

// PendingFor is every pending assignment of one module to one machine, newest first.
func (i *Inventory) PendingFor(ctx context.Context, node, module string) ([]PendingAssignment, error) {
	rows, err := i.store.Pool().Query(ctx, `select `+pendingColumns+`
		from pending_assignment p join node n on n.id = p.node
		where n.name = $1 and p.module = $2 order by p.since desc, p.id desc`, node, module)
	if err != nil {
		return nil, err
	}
	return scanPending(rows)
}

// Stuck is every pending assignment left applying since before the time given: a controller that claimed
// it and stopped before it said what came of it.
func (i *Inventory) Stuck(ctx context.Context, before time.Time) ([]PendingAssignment, error) {
	rows, err := i.store.Pool().Query(ctx, `select `+pendingColumns+`
		from pending_assignment p join node n on n.id = p.node
		where p.state = 'applying' and p.settled_at < $1 order by p.id`, before)
	if err != nil {
		return nil, err
	}
	return scanPending(rows)
}

// ToRaise is every pending assignment that expired or was refused and has not been raised as a condition;
// ToClear every one raised and not cleared.
func (i *Inventory) ToRaise(ctx context.Context) ([]PendingAssignment, error) {
	rows, err := i.store.Pool().Query(ctx, `select `+pendingColumns+`
		from pending_assignment p join node n on n.id = p.node
		where p.state in ('expired', 'refused') and p.raised_at is null order by p.id`)
	if err != nil {
		return nil, err
	}
	return scanPending(rows)
}

func (i *Inventory) ToClear(ctx context.Context) ([]PendingAssignment, error) {
	rows, err := i.store.Pool().Query(ctx, `select `+pendingColumns+`
		from pending_assignment p join node n on n.id = p.node
		where p.raised_at is not null and p.cleared_at is null order by p.id`)
	if err != nil {
		return nil, err
	}
	return scanPending(rows)
}

// MarkPending stamps a pending assignment raised, acknowledged or cleared, now.
func (i *Inventory) MarkPending(ctx context.Context, id int64, what string) error {
	column := map[string]string{"raised": "raised_at", "acknowledged": "acknowledged_at", "cleared": "cleared_at"}[what]
	if column == "" {
		return errors.New("a pending assignment is marked raised, acknowledged or cleared")
	}
	_, err := i.store.Pool().Exec(ctx,
		`update pending_assignment set `+column+` = coalesce(`+column+`, now()) where id = $1`, id)
	return err
}

// ClaimPending takes a waiting pending assignment for making, so nothing else settles or withdraws it while
// it is made. False when it no longer waits: another process took it, or it was withdrawn.
func (i *Inventory) ClaimPending(ctx context.Context, id int64) (bool, error) {
	tag, err := i.store.Pool().Exec(ctx,
		`update pending_assignment set state = 'applying', settled_at = now() where id = $1 and state = 'waiting'`, id)
	if err != nil {
		return false, err
	}
	return tag.RowsAffected() == 1, nil
}

// ReleaseClaim puts a claimed pending assignment back to waiting.
func (i *Inventory) ReleaseClaim(ctx context.Context, id int64) error {
	_, err := i.store.Pool().Exec(ctx,
		`update pending_assignment set state = 'waiting', settled_at = null where id = $1 and state = 'applying'`, id)
	return err
}

// SettlePending ends a pending assignment in the state it is read in (from): waiting for an expiry or a
// withdrawal, applying for the outcome of making it. False when it was no longer in that state.
func (i *Inventory) SettlePending(ctx context.Context, id int64, from, state, note string) (bool, error) {
	if state == PendingWaiting || state == PendingApplying {
		return false, errors.New("a pending assignment is settled to applied, refused, expired or withdrawn")
	}
	tag, err := i.store.Pool().Exec(ctx,
		`update pending_assignment set state = $3, note = $4, settled_at = now()
		  where id = $1 and state = $2`, id, from, state, note)
	if err != nil {
		return false, err
	}
	return tag.RowsAffected() == 1, nil
}

// ForgetEndedPending deletes ended pending assignments settled more than KeptFor ago, and says how many. One
// raised as a condition is kept until that condition is cleared: deleting it would leave the condition
// with nothing to answer it.
func (i *Inventory) ForgetEndedPending(ctx context.Context, now time.Time) (int64, error) {
	tag, err := i.store.Pool().Exec(ctx,
		`delete from pending_assignment where state not in ('waiting', 'applying') and settled_at < $1
		   and (raised_at is null or cleared_at is not null)`,
		now.Add(-KeptFor))
	if err != nil {
		return 0, err
	}
	return tag.RowsAffected(), nil
}

// PendingKnown says which of these pending assignments are still on record.
func (i *Inventory) PendingKnown(ctx context.Context, ids []int64) (map[int64]bool, error) {
	rows, err := i.store.Pool().Query(ctx, `select id from pending_assignment where id = any($1)`, ids)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := map[int64]bool{}
	for rows.Next() {
		var id int64
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		out[id] = true
	}
	return out, rows.Err()
}