package inventory

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

	"github.com/jackc/pgx/v5"

	"github.com/novox/mesh-controller/internal/catalogue"
)

// The gate's verdicts (novox/hq ADR 0235, to-be 45 §8): what a build did on its first machine, and,
// for one that failed there, how it was put back. One row per build, written by the plan that rolled it
// out, under the lease.

// The gate's verdicts and a failed build's rollback.
const (
	GatePassed = "passed"
	GateFailed = "failed"

	RollingBack   = "rolling-back"
	RolledBack    = "rolled-back"
	NotRolledBack = "not-rolled-back"
)

// GateVerdict is one build's verdict at its gate.
type GateVerdict struct {
	Build     string
	Module    string
	Commit    string
	Previous  string
	Plan      string
	Machines  []string
	Verdict   string
	Rollback  string
	Why       string
	Component string
	// JudgingFrom is when the first machine reported the build applied and the judging began.
	JudgingFrom *time.Time
	JudgedAt    time.Time
	Epoch       uint64
}

// RecordGate writes a build's verdict. **A failed build's row is written once**: a second failure for
// the same build is refused with ErrGateKept, which is what keeps a rollback to one per build — the row
// is written before the rollback's send, and a controller replaced in between finds it.
func (i *Inventory) RecordGate(ctx context.Context, v GateVerdict) error {
	epoch, err := i.actingEpoch(ctx)
	if err != nil {
		return fmt.Errorf("the gate's verdict on %s is not written: %w", v.Build, err)
	}
	if v.Machines == nil {
		v.Machines = []string{}
	}
	tag, err := i.store.Pool().Exec(ctx,
		`insert into build_gate (build, module, commit_hash, previous, plan, machines, verdict, rollback, why,
		                         component, judging_from, judged_at, epoch)
		 values ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, now(), $12)
		 on conflict (build) do update set verdict = excluded.verdict, rollback = excluded.rollback,
		        why = excluded.why, previous = excluded.previous, machines = excluded.machines,
		        judged_at = now(), epoch = excluded.epoch
		  where build_gate.verdict = 'passed' and excluded.verdict = 'passed'`,
		v.Build, v.Module, v.Commit, v.Previous, v.Plan, v.Machines, v.Verdict, v.Rollback, v.Why, v.Component,
		v.JudgingFrom, epoch)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return fmt.Errorf("%w: %s", ErrGateKept, v.Build)
	}
	return nil
}

// ErrGateKept is a verdict already kept for the build, which is not written over.
var ErrGateKept = errors.New("this build's verdict at its gate is already kept")

// SetRollback records how a failed build's rollback went.
func (i *Inventory) SetRollback(ctx context.Context, build, rollback, why string) error {
	if _, err := i.actingEpoch(ctx); err != nil {
		return err
	}
	_, err := i.store.Pool().Exec(ctx,
		`update build_gate set rollback = $2, why = $3, judged_at = now() where build = $1 and verdict = 'failed'`,
		build, rollback, why)
	return err
}

// GateOf is a build's verdict, and whether it has one.
func (i *Inventory) GateOf(ctx context.Context, build string) (GateVerdict, bool, error) {
	rows, err := i.store.Pool().Query(ctx, gateSelect+` where build = $1`, build)
	if err != nil {
		return GateVerdict{}, false, err
	}
	list, err := scanGates(rows)
	if err != nil || len(list) == 0 {
		return GateVerdict{}, false, err
	}
	return list[0], true, nil
}

// GateFailed is whether a build failed its gate: one the mesh never registers or sends again on its own.
func (i *Inventory) GateFailed(ctx context.Context, build string) (bool, error) {
	v, found, err := i.GateOf(ctx, build)
	return found && v.Verdict == GateFailed, err
}

// LatestGates is the newest verdict of every module that has one: what the gate probe (DG) reads.
func (i *Inventory) LatestGates(ctx context.Context) ([]GateVerdict, error) {
	rows, err := i.store.Pool().Query(ctx, `select distinct on (module) build, module, commit_hash, previous, plan,
	        machines, verdict, rollback, why, component, judging_from, judged_at, coalesce(epoch, 0)
	   from build_gate order by module, judged_at desc`)
	if err != nil {
		return nil, err
	}
	return scanGates(rows)
}

// Gates is the newest verdicts, newest first: what `plans gates` lists.
func (i *Inventory) Gates(ctx context.Context, limit int) ([]GateVerdict, error) {
	rows, err := i.store.Pool().Query(ctx, gateSelect+` order by judged_at desc limit $1`, limit)
	if err != nil {
		return nil, err
	}
	return scanGates(rows)
}

const gateSelect = `select build, module, commit_hash, previous, plan, machines, verdict, rollback, why, component,
        judging_from, judged_at, coalesce(epoch, 0) from build_gate`

func scanGates(rows pgx.Rows) ([]GateVerdict, error) {
	defer rows.Close()
	var out []GateVerdict
	for rows.Next() {
		var v GateVerdict
		var epoch int64
		if err := rows.Scan(&v.Build, &v.Module, &v.Commit, &v.Previous, &v.Plan, &v.Machines, &v.Verdict,
			&v.Rollback, &v.Why, &v.Component, &v.JudgingFrom, &v.JudgedAt, &epoch); err != nil {
			return nil, err
		}
		v.Epoch = uint64(epoch)
		out = append(out, v)
	}
	return out, rows.Err()
}

// PreviousBuild is the build a module goes back to when a build of it fails its gate: the newest build
// that worked, made from the commit the first machine ran before, asked before the failed one, and not
// itself failed at a gate. Among the builds whose artifacts the mesh keeps (KeptBuilds): an older one
// may already be gone from the artifact store. False when there is none to go back to.
func (i *Inventory) PreviousBuild(ctx context.Context, module, commit string, failed Build) (Build, bool, error) {
	builds, err := i.Builds(ctx, module, 50)
	if err != nil {
		return Build{}, false, err
	}
	kept := 0
	for _, b := range builds {
		if !b.Worked() {
			continue
		}
		kept++
		if kept > KeptBuilds {
			break
		}
		if b.ID == failed.ID || (commit != "" && b.Commit != commit) {
			continue
		}
		if !failed.AskedOrAt().IsZero() && !b.AskedOrAt().Before(failed.AskedOrAt()) {
			continue
		}
		if bad, err := i.GateFailed(ctx, b.ID); err != nil {
			return Build{}, false, err
		} else if bad {
			continue
		}
		var manifest []byte
		if err := i.store.Pool().QueryRow(ctx, `select manifest from build where id = $1`, b.ID).Scan(&manifest); err != nil {
			return Build{}, false, err
		}
		if len(manifest) == 0 || string(manifest) == "null" {
			continue
		}
		b.Manifest = manifest
		return b, true, nil
	}
	return Build{}, false, nil
}

// RestoreModule puts a module's registered build back to an earlier one: its manifest, the commit it
// was built from, and when it was asked — as now, so the build that failed its gate, asked before, can
// never register over it again (issue 219's order). The source's head is left where the merge moved it:
// the module IS behind its source, and `status` says so.
func (i *Inventory) RestoreModule(ctx context.Context, b Build) error {
	if _, err := i.actingEpoch(ctx); err != nil {
		return fmt.Errorf("%s is not put back: %w", b.Module, err)
	}
	m, err := catalogue.ParseManifest(b.Manifest)
	if err != nil {
		return fmt.Errorf("%s's build %s is not a manifest the mesh can register again: %w", b.Module, b.ID, err)
	}
	raw, err := json.Marshal(m)
	if err != nil {
		return err
	}
	tag, err := i.store.Pool().Exec(ctx,
		`update module set manifest = $2, version = nullif($3, ''), built_from = nullif($4, ''),
		        built_asked = now(), registered = now()
		  where name = $1`, b.Module, raw, m.Version, b.Commit)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return fmt.Errorf("%w: %s", ErrNoSuchModule, b.Module)
	}
	return nil
}