package inventory

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"sort"
	"time"

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

// A node is adopted or converged (novox/hq ADR 0100).
//
// Adopted: what is found on the machine is kept until its module is taken, and the firewall found
// there stays in force. Converged: the machine is what the mesh declares, as every node was before
// adoption existed. The controller is authoritative, and every declaration it sends says which.

// ErrNotAdopted is taking a module on a node that is converged. On a converged node every assigned
// module converges already; there is nothing to take.
var ErrNotAdopted = errors.New("the node is converged, so every module on it is taken already")

// ErrNotAssigned is taking a module that is not on the node. Taking is the cutover of a module
// the node runs; one it does not run has nothing to cut over.
var ErrNotAssigned = errors.New("that module is not assigned to the node")

// SetAdopted makes a node adopted or converged. Becoming adopted stamps when; converging stamps
// when too. Neither touches what was taken: what was taken stays taken when a node returns to
// adopted, and converging takes the rest by its own act.
func (i *Inventory) SetAdopted(ctx context.Context, name string, adopted bool) error {
	node, err := i.NodeByName(ctx, name)
	if err != nil {
		return err
	}
	if node.Adopted == adopted {
		return nil
	}
	if adopted {
		_, err = i.store.Pool().Exec(ctx,
			`update node set adopted = true, adopted_since = now() where id = $1`, node.ID)
		return err
	}
	_, err = i.store.Pool().Exec(ctx,
		`update node set adopted = false, adopted_since = null, converged_at = now() where id = $1`,
		node.ID)
	return err
}

// Take records that a module has been taken on an adopted node: its cutover. From then on the
// module's resources converge on that node like any other, replacing what was found.
//
// Refused on a converged node and for a module not assigned there. Taking again is not an error;
// the first time it was taken is kept.
func (i *Inventory) Take(ctx context.Context, nodeName, module string) error {
	node, err := i.NodeByName(ctx, nodeName)
	if err != nil {
		return err
	}
	if !node.Adopted {
		return fmt.Errorf("%w: %s", ErrNotAdopted, nodeName)
	}
	return i.take(ctx, node, module)
}

// take is Take without the adopted check, for converging, which takes every assigned module in
// the same act that makes the node converged.
func (i *Inventory) take(ctx context.Context, node Node, module string) error {
	var assigned bool
	if err := i.store.Pool().QueryRow(ctx,
		`select exists (select 1 from assignment where node = $1 and module = $2)`,
		node.ID, module).Scan(&assigned); err != nil {
		return err
	}
	if !assigned {
		return fmt.Errorf("%w: %s is not on %s; assign it first", ErrNotAssigned, module, node.Name)
	}
	_, err := i.store.Pool().Exec(ctx,
		`insert into taken (node, module) values ($1, $2) on conflict do nothing`, node.ID, module)
	return err
}

// Converge makes an adopted node converged in one act: every module assigned there is taken, and
// the node is recorded converged. Returned is what this act took, in name order.
func (i *Inventory) Converge(ctx context.Context, nodeName string) ([]string, error) {
	node, err := i.NodeByName(ctx, nodeName)
	if err != nil {
		return nil, err
	}
	if !node.Adopted {
		return nil, fmt.Errorf("%s is converged already", nodeName)
	}
	tx, err := i.store.Pool().Begin(ctx)
	if err != nil {
		return nil, err
	}
	defer func() { _ = tx.Rollback(context.WithoutCancel(ctx)) }()
	rows, err := tx.Query(ctx,
		`insert into taken (node, module)
		 select node, module from assignment where node = $1
		 on conflict do nothing
		 returning module`, node.ID)
	if err != nil {
		return nil, err
	}
	var took []string
	for rows.Next() {
		var m string
		if err := rows.Scan(&m); err != nil {
			rows.Close()
			return nil, err
		}
		took = append(took, m)
	}
	rows.Close()
	if err := rows.Err(); err != nil {
		return nil, err
	}
	if _, err := tx.Exec(ctx,
		`update node set adopted = false, adopted_since = null, converged_at = now(),
		        held = null, reachable = null
		  where id = $1`,
		node.ID); err != nil {
		return nil, err
	}
	if err := tx.Commit(ctx); err != nil {
		return nil, err
	}
	sort.Strings(took)
	return took, nil
}

// Taken is every module taken on a node, in name order — including one no longer assigned there:
// unassigning does not un-take.
func (i *Inventory) Taken(ctx context.Context, nodeName string) ([]string, error) {
	node, err := i.NodeByName(ctx, nodeName)
	if err != nil {
		return nil, err
	}
	rows, err := i.store.Pool().Query(ctx,
		`select module from taken where node = $1 order by module`, node.ID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []string
	for rows.Next() {
		var m string
		if err := rows.Scan(&m); err != nil {
			return nil, err
		}
		out = append(out, m)
	}
	return out, rows.Err()
}

// Held is one file or container an adopted node found and keeps as it was until its module is
// taken. The node's own account, kept as it said it.
type Held struct {
	ID      string    `json:"id"`
	Module  string    `json:"module"`
	Kind    string    `json:"kind"`
	Target  string    `json:"target"`
	Since   time.Time `json:"since"`
	Changed string    `json:"changed,omitempty"`
	Kept    string    `json:"kept,omitempty"`
}

// Reach is one thing reachable on an adopted node: a listening socket or a published port.
type Reach struct {
	Protocol      string `json:"protocol"`
	Address       string `json:"address"`
	Port          int    `json:"port"`
	By            string `json:"by,omitempty"`
	Published     bool   `json:"published,omitempty"`
	ContainerPort int    `json:"container-port,omitempty"`
}

// Adoption is what an adopted node last said about adoption, and when.
type Adoption struct {
	Held      []Held
	Firewall  string
	Reachable []Reach
	// At is when it said so; zero when it never has.
	At time.Time
}

// RecordAdoption keeps what a node last reported about adoption, replacing what was there: the
// question is the machine as it is now.
func (i *Inventory) RecordAdoption(ctx context.Context, node string, held []Held, firewall string,
	reachable []Reach) error {
	heldRaw, err := json.Marshal(nonNil(held))
	if err != nil {
		return err
	}
	reachRaw, err := json.Marshal(nonNil(reachable))
	if err != nil {
		return err
	}
	_, err = i.store.Pool().Exec(ctx,
		`update node set held = $2, firewall = nullif($3, ''), reachable = $4,
		        adoption_reported = now(), last_seen = now()
		  where id = $1`, node, heldRaw, firewall, reachRaw)
	return err
}

func nonNil[T any](s []T) []T {
	if s == nil {
		return []T{}
	}
	return s
}

// AdoptionOf is what a node last reported about adoption.
func (i *Inventory) AdoptionOf(ctx context.Context, name string) (Adoption, error) {
	var heldRaw, reachRaw []byte
	var firewall *string
	var at *time.Time
	err := i.store.Pool().QueryRow(ctx,
		`select held, firewall, reachable, adoption_reported from node where name = $1`, name).
		Scan(&heldRaw, &firewall, &reachRaw, &at)
	if errors.Is(err, pgx.ErrNoRows) {
		return Adoption{}, fmt.Errorf("%w: %s", ErrNoSuchNode, name)
	}
	if err != nil {
		return Adoption{}, err
	}
	var out Adoption
	if firewall != nil {
		out.Firewall = *firewall
	}
	if at != nil {
		out.At = *at
	}
	if len(heldRaw) > 0 {
		if err := json.Unmarshal(heldRaw, &out.Held); err != nil {
			return Adoption{}, err
		}
	}
	if len(reachRaw) > 0 {
		if err := json.Unmarshal(reachRaw, &out.Reachable); err != nil {
			return Adoption{}, err
		}
	}
	return out, nil
}