package main

import (
	"context"
	"fmt"
	"slices"
	"time"

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

// The links a rollout makes (novox/hq ADR 0408 §1, design 47 acceptance 10, issue 1095): the send of a plan's tier puts a
// build on a machine; the assignment of the module there names the build, its commit and the rollout (written by the record of
// the send, inventory.RecordSent, from the context a send is made in), and the rollout lists the assignments it changed with the
// build before and after.

// rolloutModules is what a plan sends of each module: the commit and the build of it.
func rolloutModules(p *inventory.Plan) map[string]inventory.RolloutModule {
	out := make(map[string]inventory.RolloutModule, len(p.Modules))
	for m, s := range p.Modules {
		if s != nil && s.Commit != "" {
			out[m] = inventory.RolloutModule{Commit: s.Commit, Build: s.Build}
		}
	}
	return out
}

// sendingAs is the context a plan's send is made in: what is recorded of the send names this rollout.
func sendingAs(ctx context.Context, p *inventory.Plan) context.Context {
	return inventory.WithRollout(ctx, p.ID, rolloutModules(p))
}

// ranBefore is what each module on a machine ran before a send, as the chain names it: its assignment's build and commit,
// else the commit the machine was last sent for it. Read before the send, which writes the new ones.
func ranBefore(ctx context.Context, inv *inventory.Inventory, node string) map[string]chain.Ref {
	was := map[string]chain.Ref{}
	if sent, known, err := inv.SentBuilds(ctx, node); err == nil && known {
		for m, commit := range sent {
			was[m] = chain.Ref{Commit: commit}
		}
	}
	if ran, err := inv.AssignmentRuns(ctx, node); err == nil {
		for m, r := range ran {
			was[m] = r
		}
	}
	return was
}

// noteChanges writes into a plan that a send to a machine changed the assignments of the modules it carried: the build and
// commit before and after, the builds the rollout carried, and the step taken. A change noted already for the machine and the
// module is replaced, so a send made again says it once.
func noteChanges(p *inventory.Plan, node string, modules []string, was map[string]chain.Ref, at time.Time) {
	for _, m := range modules {
		s := p.Modules[m]
		if s == nil {
			continue
		}
		change := chain.Change{Node: node, Module: m, Before: was[m], After: chain.Ref{Build: s.Build, Commit: s.Commit}}
		if at := slices.IndexFunc(p.Changed, func(c chain.Change) bool { return c.Node == node && c.Module == m }); at >= 0 {
			change.Before = p.Changed[at].Before
			p.Changed[at] = change
		} else {
			p.Changed = append(p.Changed, change)
		}
		if s.Build != "" && !slices.Contains(p.Builds, s.Build) {
			p.Builds = append(p.Builds, s.Build)
		}
	}
	if !slices.ContainsFunc(p.Steps, func(s chain.Step) bool { return s.Tier == p.Tier && s.Node == node }) {
		sent := at.UTC()
		p.Steps = append(p.Steps, chain.Step{Tier: p.Tier, Node: node, Sent: &sent})
	}
}

// refSaid is a build and the commit it was made from as a person reads them; "nothing" for a module that ran none.
func refSaid(r chain.Ref) string {
	switch {
	case r.Build == "" && r.Commit == "":
		return "nothing"
	case r.Build == "":
		return "commit " + short(r.Commit)
	}
	return r.Build + " (" + short(r.Commit) + ")"
}

// changedLines say the assignments a rollout changed: the machine, the module, and the build before and after.
func changedLines(p inventory.Plan) []string {
	if len(p.Changed) == 0 {
		return nil
	}
	out := []string{"  changed:"}
	for _, c := range p.Changed {
		out = append(out, fmt.Sprintf("    %s/%s  %s → %s", c.Node, c.Module, refSaid(c.Before), refSaid(c.After)))
	}
	return out
}

// runLines say what each module assigned to a machine runs there, as its assignment names it: the build, the commit, the
// rollout that put it there and since when.
func runLines(assigned []chain.Assignment) []string {
	var out []string
	for _, a := range assigned {
		if a.Build == "" && a.Commit == "" {
			continue
		}
		line := fmt.Sprintf("    %-22s %s", a.Module, refSaid(chain.Ref{Build: a.Build, Commit: a.Commit}))
		if a.Rollout != "" {
			line += ", sent by " + a.Rollout
		}
		if !a.Since.IsZero() {
			line += " at " + a.Since.Local().Format("2006-01-02 15:04")
		}
		out = append(out, line)
	}
	if len(out) == 0 {
		return nil
	}
	return append([]string{"  what they run, as the chain names it:"}, out...)
}