package delivery

import (
	"encoding/json"
	"fmt"
	"reflect"
	"strings"
	"time"
)

// The checker's keys (novox/hq ADR 0447 clauses 1 to 3, ADR 0444, ADR 0446 clause 5, ADR 0453 clause 4): the verdicts of
// its checks and the passing verdicts it keeps per package and level. The checker writes them from R4c, dark, and
// writes the status `mesh/check` it decides as an owed act in its own bucket (CheckerOwedBucket, the gate's owed shape);
// the forge bridge, the only part that calls the forge, performs that act (unrequired until R4f), once per revision of
// the key (ADR 0484 clause 2). The gate reads the status from R4f, and the view and the watchman read the verdicts (a
// running check carries a pulse).
//
// **The verdict's key is the group and the heads, not the fingerprints** (the lead's limit for R4a). Research 063
// section 01 drew `verdicts.<g>.check.<fpset>`; ADR 0447 clause 1 judges a pull request's head merged onto its
// trunk's head, and a repository without modules has no fingerprint set, so the key is `<group>.<heads hash>` as the
// heads hash of HeadsHash gives it. The fpset (FingerprintSet) is not part of it.
const (
	// CheckerModule is the module of the checker part.
	CheckerModule = "mesh-delivery-checker"
	// CheckerVerdictsBucket is the checker's bucket of verdicts, `<owner module>_<name>`.
	CheckerVerdictsBucket = CheckerModule + "_verdicts"
	// CheckerVerdictsHistory is the revisions the verdicts bucket keeps per key.
	CheckerVerdictsHistory = 5
	// CheckerKeptBucket is the checker's bucket of kept verdicts. A key is written once, by a create that fails when
	// the key exists, by the checker's credential alone, from the result the checker reads from the test run and
	// never from anything the code under test writes (ADR 0444 clause 5); nothing changes it afterwards.
	CheckerKeptBucket = CheckerModule + "_kept"
	// CheckerKeptHistory is the revisions the kept bucket keeps per key.
	CheckerKeptHistory = 1
)

// The test levels (ADR 0445 clause 2) and the states of a verdict.
const (
	LevelUnit        = "unit"
	LevelIntegration = "integration"

	VerdictRunning = "running"
	VerdictPass    = "pass"
	VerdictFail    = "fail"
)

func checkLevel(level string) error {
	if level != LevelUnit && level != LevelIntegration {
		return fmt.Errorf("delivery: the level %q is not %s or %s", level, LevelUnit, LevelIntegration)
	}
	return nil
}

func isHex12(s string) bool { return len(s) == 12 && strings.Trim(s, "0123456789abcdef") == "" }

// CheckerVerdictKey is the key, in CheckerVerdictsBucket, of a group's check at its heads: `<escaped group>.<heads
// hash>`, the group escaped as CandidatesKey does and the heads hash as HeadsHash gives it (12 lowercase hex digits).
func CheckerVerdictKey(group, headsHash string) (string, error) {
	g, err := groupKey(group)
	if err != nil {
		return "", err
	}
	if !isHex12(headsHash) {
		return "", fmt.Errorf("delivery: %q is not a heads hash, 12 lowercase hex digits", headsHash)
	}
	return g + "." + headsHash, nil
}

// ParseCheckerVerdictKey is the inverse of CheckerVerdictKey.
func ParseCheckerVerdictKey(key string) (group, headsHash string, err error) {
	i := strings.LastIndex(key, ".")
	if i < 0 {
		return "", "", fmt.Errorf("delivery: %q is not a verdict key, <group>.<heads hash>", key)
	}
	part, headsHash := key[:i], key[i+1:]
	if !isHex12(headsHash) {
		return "", "", fmt.Errorf("delivery: %q is not a verdict key: %q is not a heads hash, 12 lowercase hex digits", key, headsHash)
	}
	if group, err = parseGroupKey(part); err != nil {
		return "", "", fmt.Errorf("delivery: %q is not a verdict key: %w", key, err)
	}
	if strings.Contains(part, ".") {
		return "", "", fmt.Errorf("delivery: %q is not a verdict key: the group part holds a dot", key)
	}
	return group, headsHash, nil
}

// LevelResult is a level's tests: how many ran in this check and how many were taken from kept verdicts (ADR 0444
// clause 2).
type LevelResult struct {
	Run  int `json:"run"`
	Kept int `json:"kept"`
	// Skipped is the tests the run skipped, so a pass never hides them (issue 1251, ADR 0484 clause 7).
	Skipped int `json:"skipped,omitempty"`
}

// The states of a Composition (ADR 0484 clause 6): the composition check is the assigner's, so until it delivers a
// verdict says CompositionNotRun, and a line never says the composition passed on that.
const (
	CompositionNotRun = "not-run"
	CompositionPass   = "pass"
	CompositionFail   = "fail"
)

// Composition is what the check of the machines' composition made of a verdict: its State (not-run, pass or fail), the
// Words of a refusal, the mesh-sdk commit it composed with and the machines composed (ADR 0482 clause 9, ADR 0484 clause 6).
type Composition struct {
	State    string   `json:"state"`
	Words    string   `json:"words,omitempty"`
	SDK      string   `json:"sdk,omitempty"`
	Machines []string `json:"machines,omitempty"`
}

// Took is the time of each part of a check in integer milliseconds (ADR 0447 clause 3): waiting in the queue, cloning,
// the unit level, the integration level's setup and its running, and the composition.
type Took struct {
	Queue            int64 `json:"queue"`
	Clone            int64 `json:"clone"`
	Unit             int64 `json:"unit"`
	IntegrationSetup int64 `json:"integration-setup"`
	IntegrationRun   int64 `json:"integration-run"`
	Composition      int64 `json:"composition"`
}

// FailedFirst names what failed first: a test (its package and name) or a machine (and the words of the composition's
// refusal); one of them, with Words optional.
type FailedFirst struct {
	Test    string `json:"test,omitempty"`
	Machine string `json:"machine,omitempty"`
	Words   string `json:"words,omitempty"`
}

// Verdict is the value of a verdict key: the group and its heads hash, the trunk head of each repository it was judged
// against (repository to full sha), the State (running, pass or fail), what failed first, the tests run and kept per
// level, each part's time, the machines composed and the mesh-sdk version the composition ran with (ADR 0446 clause 5).
type Verdict struct {
	V        int                    `json:"v"`
	Group    string                 `json:"group"`
	Heads    string                 `json:"heads"`
	Trunk    map[string]string      `json:"trunk,omitempty"`
	State    string                 `json:"state"`
	Failed   FailedFirst            `json:"failed,omitzero"`
	Levels   map[string]LevelResult `json:"levels,omitempty"`
	Took     Took                   `json:"took,omitzero"`
	Machines []string               `json:"machines,omitempty"`
	SDK      string                 `json:"sdk,omitempty"`
	// Composition is the composition check's result; absent in a value written before it (ADR 0484 clause 6).
	Composition *Composition `json:"composition,omitempty"`
	// OverBound names the levels whose running went over their bound; it does not change the State (ADR 0453 clause 9).
	OverBound []string `json:"over-bound,omitempty"`
}

func (c *Composition) check() error {
	if c == nil {
		return nil
	}
	switch c.State {
	case CompositionNotRun:
		if c.Words != "" || c.SDK != "" || len(c.Machines) > 0 {
			return fmt.Errorf("delivery: the verdict's composition is not run and says nothing of words, the mesh-sdk commit or machines")
		}
	case CompositionPass:
		if c.SDK == "" {
			return fmt.Errorf("delivery: the verdict's composition passed and names no mesh-sdk commit")
		}
	case CompositionFail:
		if c.Words == "" {
			return fmt.Errorf("delivery: the verdict's composition failed and gives no words")
		}
	default:
		return fmt.Errorf("delivery: the verdict's composition state %q is not %s, %s or %s", c.State, CompositionNotRun, CompositionPass, CompositionFail)
	}
	return nil
}

func (v Verdict) check() error {
	if v.Group == "" {
		return fmt.Errorf("delivery: a verdict names no group")
	}
	if !isHex12(v.Heads) {
		return fmt.Errorf("delivery: the verdict's heads hash %q is not 12 lowercase hex digits", v.Heads)
	}
	for repository, head := range v.Trunk {
		if head == "" {
			return fmt.Errorf("delivery: the verdict's trunk head of %s is empty", repository)
		}
	}
	for level, r := range v.Levels {
		if err := checkLevel(level); err != nil {
			return err
		}
		if r.Run < 0 || r.Kept < 0 || r.Skipped < 0 {
			return fmt.Errorf("delivery: the verdict's %s level counts a negative number of tests", level)
		}
	}
	if err := v.Composition.check(); err != nil {
		return err
	}
	seen := map[string]bool{}
	for _, level := range v.OverBound {
		if err := checkLevel(level); err != nil {
			return fmt.Errorf("delivery: the verdict's over-bound names: %w", err)
		}
		if seen[level] {
			return fmt.Errorf("delivery: the verdict's over-bound names the level %s twice", level)
		}
		seen[level] = true
	}
	for part, ms := range map[string]int64{"queue": v.Took.Queue, "clone": v.Took.Clone, "unit": v.Took.Unit,
		"integration-setup": v.Took.IntegrationSetup, "integration-run": v.Took.IntegrationRun, "composition": v.Took.Composition} {
		if ms < 0 {
			return fmt.Errorf("delivery: the verdict's time of the part %s is negative", part)
		}
	}
	named := v.Failed.Test != "" || v.Failed.Machine != ""
	switch v.State {
	case VerdictRunning:
		if v.Failed != (FailedFirst{}) {
			return fmt.Errorf("delivery: a running verdict names no failure")
		}
	case VerdictPass:
		if v.Failed != (FailedFirst{}) {
			return fmt.Errorf("delivery: a pass names no failure")
		}
		for _, level := range []string{LevelUnit, LevelIntegration} {
			if _, ok := v.Levels[level]; !ok {
				return fmt.Errorf("delivery: a pass says nothing of the %s level", level)
			}
		}
	case VerdictFail:
		if !named {
			return fmt.Errorf("delivery: a fail names neither a test nor a machine")
		}
	default:
		return fmt.Errorf("delivery: the verdict state %q is not running, pass or fail", v.State)
	}
	return nil
}

// EncodeVerdict is v as JSON at Version; it refuses a fail that names neither a test nor a machine, a pass without both
// levels, an unknown state or level, and a negative count or time.
func EncodeVerdict(v Verdict) ([]byte, error) {
	if err := v.check(); err != nil {
		return nil, err
	}
	v.V = Version
	return json.Marshal(v)
}

// DecodeVerdict reads a verdict; it refuses an unknown version (ErrUnknownVersion) and what EncodeVerdict refuses.
func DecodeVerdict(data []byte) (Verdict, error) {
	var v Verdict
	if err := decode(data, &v); err != nil {
		return Verdict{}, err
	}
	if err := v.check(); err != nil {
		return Verdict{}, err
	}
	return v, nil
}

// SameVerdict says whether two verdicts are the same value, so the checker writes only when they differ.
func SameVerdict(a, b Verdict) bool { return reflect.DeepEqual(a, b) }

// KeptKey is the key, in CheckerKeptBucket, of a kept verdict: `<level>.<digest>`, the level unit or integration (ADR
// 0445 clause 2) and the digest, lowercase hex, of everything that package's tests read at that level as the
// language's build module names it (ADR 0444 clause 1, ADR 0445 clause 5).
func KeptKey(level, digest string) (string, error) {
	if err := checkLevel(level); err != nil {
		return "", err
	}
	if digest == "" || strings.Trim(digest, "0123456789abcdef") != "" {
		return "", fmt.Errorf("delivery: %q is not a digest, lowercase hex", digest)
	}
	return level + "." + digest, nil
}

// ParseKeptKey is the inverse of KeptKey.
func ParseKeptKey(key string) (level, digest string, err error) {
	level, digest, ok := strings.Cut(key, ".")
	if !ok {
		return "", "", fmt.Errorf("delivery: %q is not a kept key, <level>.<digest>", key)
	}
	if _, err = KeptKey(level, digest); err != nil {
		return "", "", fmt.Errorf("delivery: %q is not a kept key: %w", key, err)
	}
	return level, digest, nil
}

// Kept is the value of a kept key: a passing verdict of one package at one level (State is pass and nothing else: a
// failure is never kept, ADR 0444 clause 1), with the repository, the package, the number of tests, the time they took
// in milliseconds, the toolchain's version and when it was kept.
type Kept struct {
	V          int       `json:"v"`
	State      string    `json:"state"`
	Repository string    `json:"repository"`
	Package    string    `json:"package"`
	Level      string    `json:"level"`
	Tests      int       `json:"tests"`
	Took       int64     `json:"took"`
	Toolchain  string    `json:"toolchain"`
	At         time.Time `json:"at"`
}

func (k Kept) check() error {
	if k.State != VerdictPass {
		return fmt.Errorf("delivery: a kept verdict is a pass, never %q: a failure is never kept", k.State)
	}
	if err := checkRepository(k.Repository); err != nil {
		return err
	}
	if k.Package == "" {
		return fmt.Errorf("delivery: a kept verdict names no package")
	}
	if err := checkLevel(k.Level); err != nil {
		return err
	}
	if k.Tests < 0 || k.Took < 0 {
		return fmt.Errorf("delivery: a kept verdict counts a negative number of tests or a negative time")
	}
	if k.Toolchain == "" {
		return fmt.Errorf("delivery: a kept verdict names no toolchain version")
	}
	if k.At.IsZero() {
		return fmt.Errorf("delivery: a kept verdict says no time")
	}
	return nil
}

// EncodeKept is k as JSON at Version; it refuses a kept value that is not a pass.
func EncodeKept(k Kept) ([]byte, error) {
	if err := k.check(); err != nil {
		return nil, err
	}
	k.V = Version
	return json.Marshal(k)
}

// DecodeKept reads a kept value; it refuses an unknown version (ErrUnknownVersion) and what EncodeKept refuses.
func DecodeKept(data []byte) (Kept, error) {
	var k Kept
	if err := decode(data, &k); err != nil {
		return Kept{}, err
	}
	if err := k.check(); err != nil {
		return Kept{}, err
	}
	return k, nil
}

// SameKept says whether two kept values are the same value.
func SameKept(a, b Kept) bool {
	at := a.At.Equal(b.At)
	a.At, b.At = time.Time{}, time.Time{}
	return at && a == b
}