package buildstep

import (
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"strings"
	"time"
)

// The layouts this package reads and writes are the part `build-step`'s, shared by the three build seats'
// contracts in mesh-delivery-contracts (novox/hq ADR 0634 §6): this package imports no seat's contract, so the Go,
// image and Node build modules each use it with their own seat's, and the layout is held equal by the part's
// fixtures (a step's value decodes in both).

// Version is the layout version of a step value; a reader refuses another.
const Version = 1

// ErrUnknownVersion is what DecodeStep returns for a value whose version is missing or not Version.
var ErrUnknownVersion = errors.New("buildstep: unknown value version")

// The states of a step.
const (
	StepRunning = "running"
	StepPassed  = "passed"
	StepFailed  = "failed"
	StepRefused = "refused"
)

// StepBound is how long an asker waits for one ask's step once a build node took it (30 minutes): past it the asker
// has stopped waiting, so a key still running is nobody's.
const StepBound = 30 * time.Minute

// Step is one value of a build module's `steps` state.
type Step struct {
	V       int             `json:"v"`
	ID      string          `json:"id"`
	Tool    string          `json:"tool"`
	Node    string          `json:"node"`
	State   string          `json:"state"`
	Started time.Time       `json:"started"`
	Ended   time.Time       `json:"ended,omitzero"`
	Reason  string          `json:"reason,omitempty"`
	Result  json.RawMessage `json:"result,omitempty"`
	What    string          `json:"what,omitempty"`
	Phase   string          `json:"phase,omitempty"`
	PhaseAt time.Time       `json:"phase-at,omitzero"`
	Owner   string          `json:"owner,omitempty"`
}

var (
	nameOK   = regexp.MustCompile(`^[-/_=a-zA-Z0-9]+$`)
	stepIDOK = regexp.MustCompile(`^[a-z0-9]+$`)
	askIDOK  = regexp.MustCompile(`^[0-9a-z]{8,9}[0-9a-f]{6}$`)
)

func checkNode(node string) error {
	if node == "" || !nameOK.MatchString(node) {
		return fmt.Errorf("buildstep: the node name %q is empty or holds a dot, a wildcard, whitespace or a character a key refuses", node)
	}
	return nil
}

// StepKey is the key of a step in the steps state: `<node>.<id>`.
func StepKey(node, id string) (string, error) {
	if err := checkNode(node); err != nil {
		return "", err
	}
	if !stepIDOK.MatchString(id) {
		return "", fmt.Errorf("buildstep: the step id %q is not lower-case letters and digits", id)
	}
	return node + "." + id, nil
}

// ParseStepKey is the inverse of StepKey.
func ParseStepKey(key string) (node, id string, err error) {
	node, id, ok := strings.Cut(key, ".")
	if !ok {
		return "", "", fmt.Errorf("buildstep: %q is not a step key, <node>.<id>", key)
	}
	if _, err := StepKey(node, id); err != nil {
		return "", "", fmt.Errorf("buildstep: %q is not a step key: %w", key, err)
	}
	return node, id, nil
}

// ParseAskStepKey is ParseStepKey for the key of a pulled ask's step, whose id is the ask's (base-36 milliseconds
// and six hex digits).
func ParseAskStepKey(key string) (node, askID string, err error) {
	node, askID, err = ParseStepKey(key)
	if err != nil {
		return "", "", err
	}
	if !askIDOK.MatchString(askID) {
		return "", "", fmt.Errorf("buildstep: %q is not an ask's step key: %q is not an ask id", key, askID)
	}
	return node, askID, nil
}

func (s Step) check() error {
	if _, err := StepKey(s.Node, s.ID); err != nil {
		return err
	}
	if s.Tool == "" {
		return fmt.Errorf("buildstep: a step needs its tool")
	}
	switch s.State {
	case StepRunning, StepPassed, StepFailed, StepRefused:
	default:
		return fmt.Errorf("buildstep: the step state %q is not running, passed, failed or refused", s.State)
	}
	if len(s.Result) > 0 && !json.Valid(s.Result) {
		return fmt.Errorf("buildstep: the step's result is not JSON")
	}
	return nil
}

// EncodeStep is a step as its value, refusing one that is not whole.
func EncodeStep(s Step) ([]byte, error) {
	if err := s.check(); err != nil {
		return nil, err
	}
	s.V = Version
	return json.Marshal(s)
}

// DecodeStep reads a steps value; it refuses an unknown version (ErrUnknownVersion) and what EncodeStep refuses.
func DecodeStep(data []byte) (Step, error) {
	var probe struct {
		V *int `json:"v"`
	}
	if err := json.Unmarshal(data, &probe); err != nil {
		return Step{}, fmt.Errorf("buildstep: value is not JSON: %w", err)
	}
	if probe.V == nil || *probe.V != Version {
		return Step{}, fmt.Errorf("%w: this reader reads %d", ErrUnknownVersion, Version)
	}
	var s Step
	if err := json.Unmarshal(data, &s); err != nil {
		return Step{}, fmt.Errorf("buildstep: value does not fit its shape: %w", err)
	}
	if err := s.check(); err != nil {
		return Step{}, err
	}
	return s, nil
}

var (
	askCommitOK = regexp.MustCompile(`^[0-9a-f]{40}$`)
	// PackageSemver is a Go semantic version as a delivery group's check names a tagged version (`v0.1.15-feat-x.2`).
	PackageSemver = regexp.MustCompile(`^v(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)\.(0|[1-9][0-9]*)(-[0-9A-Za-z-]+(\.[0-9A-Za-z-]+)*)?$`)
)

// PackageVersions are the versions of the mesh packages a build or a check builds against, by package (a Go module's
// path): each a full commit or a Go semantic version.
type PackageVersions map[string]string

// Check refuses a package that is no module path or a version that is neither a full commit nor a Go semantic
// version, naming it.
func (p PackageVersions) Check() error {
	for pkg, version := range p {
		if pkg == "" || strings.ContainsAny(pkg, " \t\n@") || strings.HasPrefix(pkg, "/") {
			return fmt.Errorf("buildstep: the package %q is no module path", pkg)
		}
		if !askCommitOK.MatchString(version) && !PackageSemver.MatchString(version) {
			return fmt.Errorf("buildstep: the package %s names the version %q, which is neither a full commit nor a Go semantic version (v0.1.15-feat-x.2)", pkg, version)
		}
	}
	return nil
}

// Ask is the part of a build seat's ask that AskWhat reads: the layout is the part's `StepAsk`.
type Ask struct {
	Kind  string `json:"kind"`
	Build *struct {
		Module string         `json:"module"`
		FP     string         `json:"fp"`
		Fetch  map[string]any `json:"fetch"`
	} `json:"build"`
	Check *struct {
		Fetch  map[string]any `json:"fetch"`
		Levels []string       `json:"levels"`
		Run    string         `json:"run"`
	} `json:"check"`
	Compose *struct {
		Fetch map[string]any `json:"fetch"`
	} `json:"compose"`
}

// CheckAskID refuses an id that is no ask's: base-36 milliseconds and six hex digits, as NewID gives. Its form keeps it apart from
// a module's or a node's name in a key.
func CheckAskID(id string) error {
	if !askIDOK.MatchString(id) {
		return fmt.Errorf("buildstep: %q is not an ask id (base-36 milliseconds and six hex digits)", id)
	}
	return nil
}