package steprun

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

	sdkstep "git.novox.be/novox/mesh-delivery/modules/mesh-delivery-sdk/buildstep"
)

// **A pipeline step, run and said** (novox/hq ADR 0666 §7, §8, §17, §21; design 47 *Pipeline steps and the policy*,
// *Asked on a work queue, ended by an event*, *Carried, not run*). The runner asks one lint or test step of an artifact
// as the accepted kind step; the holder fetches the change's heads, runs the step and says its end as the seat's event
// step-ended on its own node's subject before the ask is acknowledged, so a holder restarted mid-step gets the ask again
// from its work queue and finishes it (ADR 0664 §1), its end said under the ask's id. A test step runs only the packages
// with no kept result for their digest at its level, says the others carried, and keeps what it passed; a step with
// nothing to do ends `nothing to run`, never passed; one that cannot run ends `could not run`, saying why.

// StepAnswer is what a step ask answers on its step key: the end it said.
type StepAnswer struct {
	Ended sdkstep.StepEnded `json:"ended"`
}

// LintAnswer is what a module's lint body answers: the failures of its language's lint, none when it passed, and
// Nothing when the tree holds nothing its lint reads.
type LintAnswer struct {
	Failed  []sdkstep.Failure `json:"failed,omitempty"`
	Nothing bool              `json:"nothing,omitempty"`
}

// runStep runs ask's pipeline step and says its end. A transport fault, a decline or the process stopping is handed back
// unsaid, for the bus to give the ask again, here or on another node.
func (s AskSteps) runStep(ctx context.Context, ask sdkstep.StepAsk) (any, error) {
	if s.SayStep == nil {
		return nil, Refuse("this build module says no step's end")
	}
	end, err := sdkstep.EndOf(ask, s.Node, sdkstep.OutcomePassed)
	if err != nil {
		return nil, Refuse("%v", err)
	}
	if err := s.stepOutcome(ctx, ask, &end); err != nil {
		return nil, err
	}
	if err := s.SayStep(end); err != nil {
		return nil, &sdkstep.Passing{Err: fmt.Errorf("the end of the step %s could not be said: %w", ask.ID, err)}
	}
	return StepAnswer{Ended: end}, nil
}

// stepOutcome runs the step into end; the error it answers is one that keeps the end unsaid.
func (s AskSteps) stepOutcome(ctx context.Context, ask sdkstep.StepAsk, end *sdkstep.StepEnded) error {
	var err error
	if ask.Step.Step == sdkstep.StepLint {
		err = s.lintStep(ctx, *ask.Step, end)
	} else {
		err = s.testStep(ctx, ask, end)
	}
	var dec *Declining
	switch {
	case err == nil:
		return nil
	case sdkstep.IsPassing(err), errors.As(err, &dec), ctx.Err() != nil:
		return err
	default:
		end.Outcome, end.Said = sdkstep.OutcomeCouldNotRun, err.Error()
		end.Tests, end.Carried, end.Kept = nil, nil, nil
		return nil
	}
}

// lintStep fetches the heads and runs the module's lint body over the artifact's tree.
func (s AskSteps) lintStep(ctx context.Context, run sdkstep.StepRun, end *sdkstep.StepEnded) error {
	if s.Lint == nil {
		end.Outcome = sdkstep.OutcomeNothingToRun
		return nil
	}
	if _, err := s.onToolchain(ctx, run.Toolchain); err != nil {
		return err
	}
	fetch := run.Fetch
	_, f, err := s.fetch(ctx, &fetch)
	if err != nil {
		return err
	}
	defer s.release(f.Workspace)
	if len(f.Conflicts) > 0 {
		return fmt.Errorf("the heads do not merge: %s", strings.Join(f.Conflicts, ", "))
	}
	Phase(ctx, "lint")
	out, err := s.Lint(ctx, map[string]any{"workspace": f.Workspace, "dir": fetch.Dir})
	if err != nil {
		return err
	}
	r, err := raw(out)
	if err != nil {
		return err
	}
	var la LintAnswer
	if err := json.Unmarshal(r, &la); err != nil {
		return fmt.Errorf("the lint answered what is not a lint answer: %s: %w", r, err)
	}
	switch {
	case len(la.Failed) > 0:
		end.Outcome, end.Said = sdkstep.OutcomeFailed, failedSaid(la.Failed)
	case la.Nothing:
		end.Outcome = sdkstep.OutcomeNothingToRun
	default:
		end.Outcome = sdkstep.OutcomePassed
	}
	return nil
}

// testStep runs one test level as a check of that level alone, taking the step's kept results in the checker's place.
func (s AskSteps) testStep(ctx context.Context, ask sdkstep.StepAsk, end *sdkstep.StepEnded) error {
	run := *ask.Step
	level := run.Step
	s.Kept = func(_ context.Context, lvl, digest string) (int, bool, error) {
		for _, k := range run.Kept {
			if k.Level == lvl && k.Digest == digest {
				return 0, true, nil
			}
		}
		return 0, false, nil
	}
	job := sdkstep.CheckJob{Fetch: *withPackages(&run.Fetch, ask.Packages), Levels: []string{level}, Kept: true, Toolchain: run.Toolchain}
	out, err := s.check(ctx, job)
	if err != nil {
		return err
	}
	answer, _ := out.(sdkstep.CheckAnswer)
	if len(answer.Levels) == 0 {
		var conflicts struct {
			Conflicts []string `json:"conflicts"`
		}
		_ = json.Unmarshal(mustRaw(answer.Fetch), &conflicts)
		return fmt.Errorf("the heads do not merge: %s", strings.Join(conflicts.Conflicts, ", "))
	}
	la := answer.Levels[0]
	if len(la.Unmet) > 0 {
		var what []string
		for _, u := range la.Unmet {
			what = append(what, u.Package+" ("+strings.Join(u.Needs, ", ")+")")
		}
		return fmt.Errorf("the %s tests of %s need what this node lacks", level, strings.Join(what, ", "))
	}
	tests, passed, ran := 0, true, false
	var why []string
	for _, t := range la.Tests {
		var tr struct {
			Passed  bool   `json:"passed"`
			Tests   int    `json:"tests"`
			NoTests bool   `json:"no_tests"`
			Why     string `json:"why"`
		}
		if err := json.Unmarshal(t, &tr); err != nil {
			return fmt.Errorf("the %s level answered what is no test result: %w", level, err)
		}
		tests += tr.Tests
		ran = ran || (!tr.NoTests && tr.Tests > 0) || !tr.Passed
		if !tr.Passed {
			passed = false
			if tr.Why != "" {
				why = append(why, tr.Why)
			}
		}
	}
	for _, k := range la.Kept {
		end.Carried = append(end.Carried, keptOf(run, k.Package, k.Digest))
	}
	switch {
	case !passed:
		end.Outcome, end.Said = sdkstep.OutcomeFailed, strings.Join(why, "; ")
		if end.Said == "" {
			end.Said = "the " + level + " tests failed"
		}
	case !ran && len(end.Carried) == 0:
		end.Outcome = sdkstep.OutcomeNothingToRun
	default:
		end.Outcome = sdkstep.OutcomePassed
		if la.Digest != nil {
			for _, p := range la.Digest.Packages {
				if !carried(end.Carried, p.Package) {
					end.Kept = append(end.Kept, keptOf(run, p.Package, p.Digest))
				}
			}
		}
	}
	if end.Outcome != sdkstep.OutcomeNothingToRun {
		end.Tests = &sdkstep.TestCounts{}
		if level == sdkstep.StepUnit {
			end.Tests.Unit = tests
		} else {
			end.Tests.Integration = tests
		}
	}
	return nil
}

func keptOf(run sdkstep.StepRun, pkg, digest string) sdkstep.KeptResult {
	return sdkstep.KeptResult{Package: pkg, Digest: digest, Level: run.Step, Toolchain: run.Toolchain, Pipeline: run.Pipeline}
}

func carried(kept []sdkstep.KeptResult, pkg string) bool {
	for _, k := range kept {
		if k.Package == pkg {
			return true
		}
	}
	return false
}

func mustRaw(v any) json.RawMessage {
	r, _ := raw(v)
	return r
}

// failedSaid names each failure in one line, the first ten.
func failedSaid(failed []sdkstep.Failure) string {
	var names []string
	for i, f := range failed {
		if i == 10 {
			names = append(names, fmt.Sprintf("and %d more", len(failed)-10))
			break
		}
		names = append(names, strings.TrimSpace(f.Package+" "+f.Test+": "+firstOf(f.Cause)))
	}
	return fmt.Sprintf("%d failed: %s", len(failed), strings.Join(names, "; "))
}

func firstOf(s string) string {
	l, _, _ := strings.Cut(strings.TrimSpace(s), "\n")
	return l
}

// SayStepOn is a holder's SayStep: the end, encoded and checked by the domain SDK (sdkstep.EncodeStepEnded), published
// on the language's build seat's step-ended subject of node with publish (stdio.SeatPublish), de-duplicated by the
// ask's id, so a step run again after a restart is said once.
func SayStepOn(language, node string, publish func(subject string, body any, id string) error) func(sdkstep.StepEnded) error {
	return func(end sdkstep.StepEnded) error {
		subject, err := sdkstep.StepEndedSubject(language, node)
		if err != nil {
			return err
		}
		body, err := sdkstep.EncodeStepEnded(end)
		if err != nil {
			return err
		}
		return publish(subject, json.RawMessage(body), "step-ended."+end.ID)
	}
}