package main

import (
	"context"
	"errors"
	"fmt"
	"regexp"
	"sort"
	"strings"
	"time"

	"github.com/novox/mesh-controller/internal/conditions"
	"github.com/novox/mesh-controller/internal/inventory"
)

// failedModule is one module of a failed plan that failed to build, where it runs and what it said.
type failedModule struct {
	module   string
	machines []string
	why      string
}

// failedPlanFacts is one failed delivery plan asked of the operator (S23, novox/hq ADR 0449 §1).
type failedPlanFacts struct {
	id, repository, commit string
	modules                []string
	failed                 []failedModule
	// note is where the plan stopped when no module failed to build (a rollout stopped at its first machine).
	note string
	// since is the plan's last change: when it failed.
	since time.Time
	// refusal is why `plans retry` would not run it, empty when it would.
	refusal string
	// passed is set when a newer plan of its repository and branch is done and the retry is refused for that
	// (novox/hq ADR 0451): the condition asks nothing.
	passed bool
}

// machines are the machines the failed modules run on, sorted, each once.
func (p failedPlanFacts) machines() []string {
	seen := map[string]bool{}
	var out []string
	for _, m := range p.failed {
		for _, n := range m.machines {
			if !seen[n] {
				seen[n] = true
				out = append(out, n)
			}
		}
	}
	sort.Strings(out)
	return out
}

// failureSaid is what failed, in the mesh's own words, for the condition's evidence.
func (p failedPlanFacts) failureSaid() string {
	var parts []string
	for _, m := range p.failed {
		line := m.module
		if len(m.machines) > 0 {
			line += " on " + strings.Join(m.machines, ", ")
		}
		if m.why != "" {
			line += ": " + oneLine(m.why)
		}
		parts = append(parts, line)
	}
	if len(parts) == 0 {
		return "stopped: " + oneLine(p.note)
	}
	return strings.Join(parts, "; ")
}

// refusalSaid is why a retry would not run, for the evidence.
func (p failedPlanFacts) refusalSaid() string {
	if p.refusal == "" {
		return ""
	}
	return "; a retry would not run: " + oneLine(p.refusal)
}

// retryAction is the one answer a failed plan offers: the controller's `plans` verb with `retry` naming the plan,
// at the level approve. Only that argument: `plans` refuses a retry that carries others (seatverbs).
func retryAction(plan string) conditions.Action {
	return conditions.Action{Label: "Retry", Verb: "mesh-controller.plans", Level: conditions.LevelApprove,
		Arguments: map[string]string{"retry": plan}}
}

var (
	planIDWord = regexp.MustCompile(`\bplan-[0-9]+\b`)
	walkWd     = regexp.MustCompile(`\bwalks\b`)
	walkOne    = regexp.MustCompile(`\bwalk\b`)
)

// plainRefusal is a retry's refusal in words the operator reads: the plans named as "the plan", a walk said as a
// delivery. Whatever still breaks the plain rule (a hash, a dotted name) is left to the condition's evidence, and the
// words say only that a retry would not run.
func plainRefusal(refusal string) string {
	return plainRefusalOr(refusal, "a retry would not run now; the details say why")
}

// plainRefusalOr is plainRefusal with the sentence to say when the refusal's own words cannot be said plainly.
func plainRefusalOr(refusal, fallback string) string {
	r := planIDWord.ReplaceAllString(refusal, "the plan")
	r = walkWd.ReplaceAllString(r, "deliveries")
	r = walkOne.ReplaceAllString(r, "delivery")
	r = strings.TrimSpace(r)
	if _, ok := conditions.Plain(r); !ok {
		return fallback
	}
	return r
}

// planFailedWords are the plain words of a failed plan: which modules failed and where, what they said when that
// is plain, and Retry when a retry would run, else the refusal's words.
func planFailedWords(p failedPlanFacts) (headline, explanation, needs string, actions []conditions.Action, resolved string) {
	name := deliveryName(p.modules, p.repository)
	headline = conditions.Capital(name) + " failed"
	what := deliveryWhat(p.modules, p.repository)
	var parts []string
	for i, m := range p.failed {
		if i == 2 {
			parts = append(parts, fmt.Sprintf("%d more", len(p.failed)-2))
			break
		}
		line := m.module
		if len(m.machines) > 0 {
			line += " for " + readableList(m.machines)
		}
		if w := strings.TrimRight(cutWords(oneLine(m.why), 110), ".;:, "); w != "" {
			if _, ok := conditions.Plain(w); ok {
				line += " (" + w + ")"
			}
		}
		parts = append(parts, line)
	}
	if len(parts) > 0 {
		explanation = fmt.Sprintf("The delivery of %s failed: %s did not build.", what, readableList(parts))
	} else {
		explanation = fmt.Sprintf("The delivery of %s stopped before it finished.", what)
	}
	switch {
	case p.passed:
		explanation += " A newer delivery has passed it, so a retry would send older code. Nothing is needed from you."
	case p.refusal == "":
		explanation += " Nothing is tried again until you say so."
		needs = "try the failed builds again " + FromMeshMCPServer
		actions = []conditions.Action{retryAction(p.id)}
	default:
		explanation += " " + conditions.Capital(plainRefusal(p.refusal)) + "."
		needs = "look at why it failed; a retry would not run now."
	}
	resolved = conditions.Capital(name) + " is no longer failed"
	return
}

// cutWords is s cut to at most n bytes at a word.
func cutWords(s string, n int) string {
	if len(s) <= n {
		return s
	}
	t := s[:n]
	if i := strings.LastIndexByte(t, ' '); i > n/2 {
		t = t[:i]
	}
	return strings.TrimRight(t, " ,;:") + "…"
}

// gatherFailedPlans is every delivery plan that failed within planFailedWithin and is asked of the operator
// (S23, novox/hq ADR 0449 §1): a failed plan that carries a delivery, is no rollout of held updates and was not
// stopped by a person. Each carries why `plans retry` would not run it, when it would not.
func gatherFailedPlans(ctx context.Context, inv *inventory.Inventory, now time.Time) ([]failedPlanFacts, error) {
	plans, err := inv.PlansSince(ctx, now.Add(-planFailedWithin))
	if err != nil {
		return nil, fmt.Errorf("the plans cannot be read: %w", err)
	}
	var failed []inventory.Plan
	for _, p := range plans {
		if failedAndAsked(p) {
			failed = append(failed, p)
		}
	}
	if len(failed) == 0 {
		return nil, nil
	}
	entries, err := inv.Catalogued(ctx)
	if err != nil {
		return nil, fmt.Errorf("the catalogue cannot be read: %w", err)
	}
	onPath := ownPathOf(entries)
	runsOn := map[string][]string{}
	for _, e := range entries {
		runsOn[e.Manifest.Module] = e.On
	}
	var out []failedPlanFacts
	for _, p := range failed {
		out = append(out, failedFactsOf(p, plans, onPath, runsOn))
	}
	return out, nil
}

// failedAndAsked says a plan is one S23 asks about: failed, a delivery's, not a rollout of held updates, not
// stopped by a person.
func failedAndAsked(p inventory.Plan) bool {
	return p.State == inventory.PlanFailed && p.Delivery != nil && p.Release == nil && p.Delivery.Stopped == ""
}

// failedFactsOf is what S23 says of one failed plan, given every plan, the controller's own path and where each
// module runs.
func failedFactsOf(p inventory.Plan, plans []inventory.Plan, onPath map[string]string,
	runsOn map[string][]string) failedPlanFacts {
	f := failedPlanFacts{id: p.ID, repository: p.Repository, commit: p.Commit, modules: planModules(p),
		note: p.Note, since: p.Updated}
	for _, m := range f.modules {
		if s := p.Modules[m]; s != nil && s.State == "failed" {
			machines := append([]string(nil), runsOn[m]...)
			sort.Strings(machines)
			f.failed = append(f.failed, failedModule{module: m, machines: machines, why: s.Why})
		}
	}
	if err := retryRefusal(p, plans, onPath); err != nil {
		f.refusal = err.Error()
		var passed passedBy
		f.passed = errors.As(err, &passed)
	}
	return f
}