package check

import (
	"encoding/json"
	"fmt"
	"sort"
	"strings"

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

// The read tools (novox/hq ADR 0484 clauses 8 and 13, issue 1686): what the checker stored, as stored, with the line of the
// status it owes in full, so a check is read live without a shell. They write nothing.

// The read tools, named as the module is: checker_ and the noun.
const (
	VerdictsReadTool = "checker_verdicts"
	PullReadTool     = "checker_pull"
	KeptReadTool     = "checker_kept"
)

// StateRead reads one state: its keys and a key's stored value (nil for a key with none).
type StateRead struct {
	Keys func() ([]string, error)
	Get  func(key string) (json.RawMessage, error)
}

// Reader answers the read tools from the checker's verdicts and kept states and the indexer's candidates.
type Reader struct{ VerdictState, KeptState, CandidateState StateRead }

// VerdictRead is a verdict as stored with the full report of the status of each pull request it judged (Report), when the
// candidate still holds those heads; without it the report is that of the verdict alone.
type VerdictRead struct {
	Key     string            `json:"key"`
	Verdict json.RawMessage   `json:"verdict"`
	Reports map[string]string `json:"reports,omitempty"`
	Note    string            `json:"note,omitempty"`
}

func (r Reader) candidate(group string) (delivery.Candidate, bool) {
	key, err := delivery.CandidatesKey(group)
	if err != nil || r.CandidateState.Get == nil {
		return delivery.Candidate{}, false
	}
	raw, err := r.CandidateState.Get(key)
	if err != nil || len(raw) == 0 {
		return delivery.Candidate{}, false
	}
	c, err := delivery.DecodeCandidate(raw)
	return c, err == nil
}

func (r Reader) read(key string, raw json.RawMessage) (VerdictRead, error) {
	out := VerdictRead{Key: key, Verdict: raw}
	v, err := delivery.DecodeVerdict(raw)
	if err != nil {
		return out, fmt.Errorf("%s holds what is not a verdict: %w", key, err)
	}
	c, ok := r.candidate(v.Group)
	if !ok || c.HeadsHash != v.Heads {
		out.Note = "the candidate no longer holds these heads"
		return out, nil
	}
	cs := CaseOf(c, v.Trunk)
	out.Reports = map[string]string{}
	if cs == nil {
		return out, nil
	}
	for _, p := range cs.Pulls {
		out.Reports[fmt.Sprintf("%s#%d", p.Repository, p.Number)] = Report(v, cs, p, nil, nil)
	}
	for _, l := range cs.Left {
		out.Reports[strings.SplitN(l, ": ", 2)[0]] = strings.SplitN(l, ": ", 2)[1]
	}
	return out, nil
}

// Verdicts are the verdicts the checker holds, by key; with a group only that group's.
func (r Reader) Verdicts(group string) ([]VerdictRead, error) {
	if r.VerdictState.Keys == nil || r.VerdictState.Get == nil {
		return nil, fmt.Errorf("the verdicts state cannot be read here")
	}
	keys, err := r.VerdictState.Keys()
	if err != nil {
		return nil, err
	}
	sort.Strings(keys)
	var out []VerdictRead
	for _, k := range keys {
		if group != "" {
			if g, _, err := delivery.ParseCheckerVerdictKey(k); err != nil || g != group {
				continue
			}
		}
		raw, err := r.VerdictState.Get(k)
		if err != nil {
			return nil, err
		}
		if len(raw) == 0 {
			continue
		}
		vr, err := r.read(k, raw)
		if err != nil {
			return nil, err
		}
		out = append(out, vr)
	}
	return out, nil
}

// Pull answers for one pull request: the verdict of the candidate that holds it, with its report; for an hq pull request,
// that hq is judged by merge-check.sh until issue 1296 (HQNote); for one the indexer holds in no candidate, that none does.
func (r Reader) Pull(repository string, number int) (VerdictRead, error) {
	if r.CandidateState.Keys == nil || r.CandidateState.Get == nil {
		return VerdictRead{}, fmt.Errorf("the candidates state cannot be read here")
	}
	keys, err := r.CandidateState.Keys()
	if err != nil {
		return VerdictRead{}, err
	}
	sort.Strings(keys)
	for _, k := range keys {
		raw, err := r.CandidateState.Get(k)
		if err != nil || len(raw) == 0 {
			continue
		}
		c, err := delivery.DecodeCandidate(raw)
		if err != nil {
			continue
		}
		for _, p := range c.Pulls {
			if p.Repository != repository || p.Number != number {
				continue
			}
			if repository == HQRepository {
				return VerdictRead{Key: k, Note: HQNote}, nil
			}
			vkey, err := delivery.CheckerVerdictKey(c.Group, c.HeadsHash)
			if err != nil {
				return VerdictRead{}, err
			}
			vraw, err := r.VerdictState.Get(vkey)
			if err != nil {
				return VerdictRead{}, err
			}
			if len(vraw) == 0 {
				return VerdictRead{Key: vkey, Note: "no verdict yet for the heads of its candidate"}, nil
			}
			return r.read(vkey, vraw)
		}
	}
	return VerdictRead{}, fmt.Errorf("no candidate holds %s#%d", repository, number)
}

// Kept is the kept verdicts: one key's value as stored, or with an empty key the keys of a level (or every level) and their values.
func (r Reader) Kept(level, digest string) (map[string]json.RawMessage, error) {
	if r.KeptState.Keys == nil || r.KeptState.Get == nil {
		return nil, fmt.Errorf("the kept state cannot be read here")
	}
	if digest != "" {
		key, err := delivery.KeptKey(level, digest)
		if err != nil {
			return nil, err
		}
		raw, err := r.KeptState.Get(key)
		if err != nil {
			return nil, err
		}
		if len(raw) == 0 {
			return nil, fmt.Errorf("no kept verdict %s", key)
		}
		return map[string]json.RawMessage{key: raw}, nil
	}
	keys, err := r.KeptState.Keys()
	if err != nil {
		return nil, err
	}
	sort.Strings(keys)
	out := map[string]json.RawMessage{}
	for _, k := range keys {
		if l, _, err := delivery.ParseKeptKey(k); err != nil || (level != "" && l != level) {
			continue
		}
		raw, err := r.KeptState.Get(k)
		if err != nil {
			return nil, err
		}
		if len(raw) > 0 {
			out[k] = raw
		}
	}
	return out, nil
}