package main

// A fix whose pull request the tracker keeps no record for (merged before the tracker heard the delivery, or linked after it
// moved) learns its merge here, so the view's `delivered` event can cover it like any recorded fix (issue 1950). The delivery
// is asked first (its `checks` carries the forge's own pull request beside its delivery); the forge is asked when the delivery
// cannot say. One that neither can say is left for the next time and logged; a pull request closed without merging becomes
// the withdrawn state the tracker already knows.

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

	stdio "git.novox.be/novox/mesh-sdk/go"
)

// pullFacts reads the forge's pull request block, as gitea_get_pull_request and mesh-delivery's checks both carry it.
type pullFacts struct {
	Merged         bool       `json:"merged"`
	State          string     `json:"state"`
	MergeCommitSHA string     `json:"merge_commit_sha"`
	MergedAt       *time.Time `json:"merged_at"`
}

// fromPull completes a delivery with what the forge's pull request says: whether it is merged or closed, the commit its
// merge landed as and when.
func (d *Delivery) fromPull(p pullFacts, repository string) {
	d.Pulled = true
	d.Merged = p.Merged
	d.Closed = p.State == "closed" && !p.Merged
	if d.Repository == "" {
		d.Repository = strings.ToLower(repository)
	}
	if p.Merged {
		if d.MergedAs == "" {
			d.MergedAs = p.MergeCommitSHA
		}
		if d.MergedAt == nil {
			d.MergedAt = nonZero(p.MergedAt)
		}
	}
}

// busPull asks the forge for one pull request (gitea_get_pull_request).
func busPull(owner string) DeliveryState {
	return func(repository, number string) (Delivery, error) {
		var n int
		if _, err := fmt.Sscanf(number, "%d", &n); err != nil || n <= 0 {
			return Delivery{}, fmt.Errorf("%q is not a pull request number", number)
		}
		raw, err := stdio.Ask("gitea.gitea_get_pull_request", map[string]any{"owner": owner, "repo": repository, "number": n})
		if err != nil {
			return Delivery{}, err
		}
		var out struct {
			Pull   *pullFacts `json:"pull"`
			Answer struct {
				Pull *pullFacts `json:"pull"`
			} `json:"answer"`
		}
		if json.Unmarshal(raw, &out) != nil {
			return Delivery{}, errors.New("the forge's gitea_get_pull_request is not readable")
		}
		p := out.Pull
		if p == nil {
			p = out.Answer.Pull
		}
		if p == nil {
			return Delivery{}, errors.New("the forge's gitea_get_pull_request answered no pull request")
		}
		var d Delivery
		d.fromPull(*p, owner+"/"+repository)
		return d, nil
	}
}

// learnFix gives a pull request an issue names and keeps no Fix record for its record: from the delivery's own state when it has
// one, else from the pull request itself (the delivery's, then the forge's). It answers whether a record was kept. A pull request
// still open is not kept (its own events say it when they come); one neither can say anything of is left for next time.
func (t *Tracker) learnFix(n uint64, pr string) (bool, error) {
	repo, number, _ := strings.Cut(pr, "#")
	var d Delivery
	var derr error
	if t.Deliveries != nil {
		d, derr = t.Deliveries(repo, number)
	}
	if derr == nil && d.State != "" {
		since := d.Since
		if since.IsZero() {
			since = t.now()
		}
		ch, err := t.recordFix(pr, d.heard(since), n)
		return len(ch) > 0, err
	}
	if derr != nil || !d.Pulled {
		if t.Pull == nil {
			return false, derr
		}
		f, ferr := t.Pull(repo, number)
		if ferr != nil {
			if derr != nil {
				return false, derr
			}
			t.Logf("[mesh-issues] the pull request %s (issue %d) could not be read from the forge (asked again later): %v", pr, n, ferr)
			return false, nil
		}
		d = f
	}
	var h heardFix
	switch {
	case d.Merged:
		// Kept as of now, the moment it was learned: the fix's state did not change days ago for the tracker, and the stuck
		// sweep measures from it. MergedAt stays the forge's own moment.
		h = heardFix{State: "merged", Merged: true, At: t.now(), MergedAt: d.MergedAt, Repository: d.Repository, MergedAs: d.MergedAs}
	case d.Closed:
		h = heardFix{State: "closed", Why: "closed without merging", At: t.now()}
	default:
		return false, nil
	}
	ch, err := t.recordFix(pr, h, n)
	return len(ch) > 0, err
}

// learnUnheard learns, for at most most pull requests, each fix of issue n with no record; it answers whether any was kept.
func (t *Tracker) learnUnheard(n uint64, is *Issue, most int) (int, bool, error) {
	asked, kept := 0, false
	for _, pr := range fixPullRequests(is) {
		if fixOf(is, pr) != nil {
			continue
		}
		if asked == most {
			break
		}
		asked++
		ok, err := t.learnFix(n, pr)
		if err != nil {
			return asked, kept, fmt.Errorf("the delivery of %s (issue %d) could not be asked: %v", pr, n, err)
		}
		kept = kept || ok
	}
	return asked, kept, nil
}

// LearnFixes is the tool that asks again for one issue: every pull request its fixed-by names with no record is asked of the
// delivery and the forge now. It answers what each is kept as.
func (t *Tracker) LearnFixes(n uint64) (map[string]any, error) {
	is, _, err := read(t.Store, n)
	if err != nil {
		return nil, err
	}
	if _, _, err := t.learnUnheard(n, is, MostSweepAsks*2); err != nil {
		return nil, err
	}
	if err := t.coverReached(); err != nil {
		return nil, err
	}
	if err := t.afterFix(n); err != nil {
		return nil, err
	}
	is, _, err = read(t.Store, n)
	if err != nil {
		return nil, err
	}
	out := map[string]string{}
	for _, pr := range fixPullRequests(is) {
		switch f := fixOf(is, pr); {
		case f == nil:
			out[pr] = "nothing heard: neither the delivery nor the forge said"
		case withdrawn(f):
			out[pr] = "withdrawn: closed without merging"
		case contains(is.Delivered, pr):
			out[pr] = "delivered"
		case f.Merged:
			out[pr] = "merged as " + shortCommit(f.MergedAs) + ", not delivered"
		default:
			out[pr] = f.State
		}
	}
	return map[string]any{"number": n, "fixes": out, "delivery": DeliveryLine(is)}, nil
}