package delivery

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

// StepsState is the name of the state a build module keeps its long steps in; its bucket is `<module>_steps`, built
// by StepsBucket (novox/hq ADR 0469 clause 2; issue 1471). A tool call is cut at 30 s, so a fetch, a test level or a
// build answers at once with a step id and writes its progress and its end to the key `<node>.<step id>`.
const StepsState = "steps"

// StepsBucket is the bucket of a build module's steps.
func StepsBucket(module string) string { return module + "_" + StepsState }

// The states of a step. A step ends in passed, failed or refused; its key is written for each of them, and that
// write is the event the step's reader waits on.
const (
	StepRunning = "running"
	StepPassed  = "passed"
	StepFailed  = "failed"
	StepRefused = "refused"
)

var stepIDOK = regexp.MustCompile(`^[a-z0-9]+$`)

func checkStepID(id string) error {
	if !stepIDOK.MatchString(id) {
		return fmt.Errorf("delivery: the step id %q is not lower-case letters and digits", id)
	}
	return nil
}

// StepKey is the key of a node's step: `<node>.<id>`. It refuses a node that is not a name and an id that is not
// lower-case letters and digits (one key token, never a dot).
func StepKey(node, id string) (string, error) {
	if err := checkName("node", node); err != nil {
		return "", err
	}
	if err := checkStepID(id); err != nil {
		return "", err
	}
	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("delivery: %q is not a step key, <node>.<id>", key)
	}
	if _, err := StepKey(node, id); err != nil {
		return "", "", fmt.Errorf("delivery: %q is not a step key: %w", key, err)
	}
	return node, id, nil
}

// Step is the value of a steps key: which tool runs on which node, how far it is, when it started and ended (UTC, as
// the toolchains' At), why it was refused or failed, and what it returned.
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"`
}

func (s Step) check() error {
	if err := checkStepID(s.ID); err != nil {
		return err
	}
	if err := checkName("node", s.Node); err != nil {
		return err
	}
	if s.Tool == "" {
		return fmt.Errorf("delivery: a step needs its tool")
	}
	switch s.State {
	case StepRunning, StepPassed, StepFailed, StepRefused:
	default:
		return fmt.Errorf("delivery: 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("delivery: the step's result is not JSON")
	}
	return nil
}

// EncodeStep is s as JSON at Version; it refuses an id that is not one key token, a node that is not a name, an empty
// tool, a state outside the four and a result that is not JSON.
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 s Step
	if err := decode(data, &s); err != nil {
		return Step{}, err
	}
	if err := s.check(); err != nil {
		return Step{}, err
	}
	return s, nil
}