package builder

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"github.com/novox/mesh-controller/internal/catalogue"
)

// The builds a merge check makes for its merge (novox/hq ADR 0350 §1): every artifact of every module the delivery
// plan moves, built from the merged tree the check judged into the scratch namespace, kept under its reuse key, so
// the walk of the merge commit takes it instead of building again. Built after the check has judged, and only when
// it did not fail: a change that fails is not merged, and nothing it built would be taken.

// CheckBuildSpec is one module a check builds for its merge, in the walk's order (Tier).
type CheckBuildSpec struct {
	Module string
	// Repository, Path and Ref are where it is built from; Merged says from the merge the check made instead — the
	// module is built from the repository checked, at the branch merged into.
	Repository string
	Path       string
	Ref        string
	Merged     bool
	Tier       int
	// Skip says why it cannot be built as the walk would build it: not built, and nothing after it.
	Skip string
}

// CheckBuilding is what a check builds with: where it publishes and keeps its builds, and what a build is handed.
type CheckBuilding struct {
	Publish Publisher
	Scratch Scratch
	Held    map[string]string
	Npmrc   Npmrc
	Seats   map[string]string
	// Named are the builds the build seat's verdicts of earlier checks of this pull request at this head name
	// (novox/hq issue 703): a build kept under a module's key is kept again, instead of built, only when one of them
	// names its key and every digest, and the build is this pull request's at this head. The record alone is never
	// enough.
	Named []NamedBuild
}

// CheckBuilt is one module a check built for its merge, as its verdict lists it (§1): its key and its artifacts, or
// why it was not built.
type CheckBuilt struct {
	Module string
	Key    string
	Made   []catalogue.Built
	// NotBuilt says why it was not: no key, a build that failed, or a module after one of those.
	NotBuilt string
	Took     time.Duration
	// Kept is the check whose build this check kept instead of building, its key unchanged (novox/hq issue 703):
	// the verdict names that build, by key and digest, as that check's. Empty when this check built it.
	Kept string
}

// skipsTheBuilds is why a check builds nothing for its merge; empty when it builds.
func skipsTheBuilds(v CheckVerdict) string {
	for _, l := range []*Layer{v.Gate, v.Repo} {
		if l != nil && (l.Verdict == "fail" || l.Verdict == "error") {
			return "the check did not pass, so nothing is built for its merge"
		}
	}
	return ""
}

// buildForTheMerge builds each module the plan moves, tier by tier, into the scratch namespace, and keeps what it
// built under its keys. A module standing after one not built is not built either: what it stands on in the walk
// is not what it would stand on here. tree is the check's clone and merge the merge commit it made there; workspace
// is where each build's working copy is made, a directory the host's container engine sees at the same path — the
// builder's own workspace, never a temporary directory of its container (novox/hq issue 713).
func buildForTheMerge(ctx context.Context, run Runner, spec CheckSpec, with CheckBuilding, workspace, tree, merge string,
	judged CheckVerdict, forge GitCredential, log Log, say func(step, format string, args ...any)) []CheckBuilt {
	if len(spec.Builds) == 0 || with.Publish == nil || with.Scratch == nil {
		return nil
	}
	ref := merge
	if ref == "" {
		ref = spec.Ref
	}
	// What an earlier check left, ended before it could remove it, is not built on.
	_ = os.RemoveAll(filepath.Join(workspace, "for-the-merge"))
	held := map[string]string{}
	for k, v := range with.Held {
		held[k] = v
	}
	var out []CheckBuilt
	var kept []CheckBuild
	stopAt, stopWhy := -1, ""
	for _, b := range spec.Builds {
		began := time.Now()
		if stopAt >= 0 && b.Tier > stopAt {
			out = append(out, CheckBuilt{Module: b.Module, NotBuilt: stopWhy})
			continue
		}
		if b.Skip != "" {
			say("build", "%s not built for the merge: %s", b.Module, b.Skip)
			out = append(out, CheckBuilt{Module: b.Module, NotBuilt: b.Skip})
			if stopAt < 0 || b.Tier < stopAt {
				stopAt, stopWhy = b.Tier, "it stands after "+b.Module+", which was not built for the merge"
			}
			continue
		}
		repository, at := b.Repository, b.Ref
		if b.Merged {
			repository, at = tree, ref
		}
		say("build", "for the merge: %s (tier %d)", b.Module, b.Tier)
		var mirrored []string
		result, err := build(ctx, run, scratchPublisher{to: with.Publish}, repository, b.Path, at,
			filepath.Join(workspace, "for-the-merge"), held, with.Npmrc, forge, log, &mirrored,
			&Reuse{keyFirst: true, Scratch: with.Scratch, Named: with.Named,
				pull: PullRef{Owner: spec.Owner, Repo: spec.Repo, Number: spec.Number}, head: judged.Head}, with.Seats)
		built := CheckBuilt{Module: b.Module, Key: result.ReuseKey, Took: time.Since(began)}
		switch {
		case errors.Is(err, errNoKey):
			built.NotBuilt = err.Error()
		case err != nil:
			built.NotBuilt = "its build failed: " + err.Error()
		case result.ReuseKey == "":
			built.NotBuilt = "it has no reuse key: " + result.NoKey
		}
		if built.NotBuilt != "" {
			say("build", "%s not built for the merge: %s", b.Module, built.NotBuilt)
			out = append(out, built)
			if stopAt < 0 || b.Tier < stopAt {
				stopAt, stopWhy = b.Tier, "it stands after "+b.Module+", which was not built for the merge"
			}
			continue
		}
		built.Made = result.Built
		for _, m := range result.Built {
			held[b.Module+"/"+m.Name] = m.Reference
		}
		if result.Reused != nil {
			// **Kept, not built** (novox/hq issue 703): the earlier check's build, named as that check's, so the
			// walk takes it as the verdict names it; this check's document names it too, so it stays while this
			// check does (ADR 0350 §5).
			built.Kept = result.Reused.From.Check
			say("build", "%s kept for the merge under %s: %s", b.Module, twelve(result.ReuseKey[3:]),
				result.Reused.From.Said())
			out = append(out, built)
			kept = append(kept, result.Reused.From)
			continue
		}
		say("build", "%s built for the merge under %s (%s)", b.Module, twelve(result.ReuseKey[3:]), built.Took.Round(time.Second))
		out = append(out, built)
		if len(result.Built) > 0 {
			kept = append(kept, CheckBuild{Key: result.ReuseKey, Module: b.Module, Parts: result.ReuseParts,
				Made: result.Built, Pull: PullRef{Owner: spec.Owner, Repo: spec.Repo, Number: spec.Number},
				Head: judged.Head, Trunk: judged.Trunk, Check: spec.ID, At: time.Now().UTC()})
		}
	}
	_ = os.RemoveAll(filepath.Join(workspace, "for-the-merge"))
	if len(kept) > 0 {
		if err := with.Scratch.Keep(ctx, PullRef{Owner: spec.Owner, Repo: spec.Repo, Number: spec.Number}, spec.ID,
			time.Now().UTC(), kept); err != nil {
			// Built and not findable: the walk builds, and says no check built it. Said, never the check's verdict.
			say("build", "the builds for the merge could not be kept, and the walk will build: %v", err)
			if err := with.Scratch.Discard(ctx, kept); err != nil {
				say("build", "and what they made could not all be let go of: %v", err)
			}
			for i := range out {
				if out[i].NotBuilt == "" {
					out[i].NotBuilt = fmt.Sprintf("built, and could not be kept: %v", err)
				}
			}
		}
	}
	return out
}