package common

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"slices"
	"strings"

	"src.opensuse.org/autogits/common/gitea-generated/client/repository"
	"src.opensuse.org/autogits/common/gitea-generated/models"
)

//go:generate mockgen -source=maintainership.go -destination=mock/maintainership.go -typed

type MaintainershipData interface {
	ListProjectMaintainers(OptionalGroupExpansion []*ReviewGroup) []string
	ListPackageMaintainers(Pkg string, OptionalGroupExpasion []*ReviewGroup) []string

	IsApproved(Pkg string, Reviews []*models.PullReview, Submitter string, ReviewGroups []*ReviewGroup) bool
}

const ProjectKey = ""
const ProjectFileKey = "_project"

type MaintainershipMap struct {
	Data         map[string][]string
	IsDir        bool
	Config       *AutogitConfig
	FetchPackage func(string) ([]byte, error)
	Raw          []byte
}

func ParseMaintainershipData(data []byte) (*MaintainershipMap, error) {
	maintainers := &MaintainershipMap{
		Data: make(map[string][]string),
		Raw:  data,
	}
	if err := json.Unmarshal(data, &maintainers.Data); err != nil {
		return nil, err
	}

	return maintainers, nil
}

func FetchProjectMaintainershipData(gitea GiteaMaintainershipReader, config *AutogitConfig) (*MaintainershipMap, error) {
	org, prjGit, branch := config.GetPrjGit()

	data, _, err := gitea.FetchMaintainershipDirFile(org, prjGit, branch, ProjectFileKey)
	dir := true
	if err != nil || data == nil {
		dir = false
		if _, notFound := err.(*repository.RepoGetContentsNotFound); !notFound {
			return nil, err
		}
		LogDebug("Falling back to maintainership file")
		data, _, err = gitea.FetchMaintainershipFile(org, prjGit, branch)
		if err != nil || data == nil {
			if _, notFound := err.(*repository.RepoGetContentsNotFound); !notFound {
				return nil, err
			}

			// no mainatiners
			data = []byte("{}")
		}
	}

	m, err := ParseMaintainershipData(data)
	if m != nil {
		m.Config = config
		m.IsDir = dir
		m.FetchPackage = func(pkg string) ([]byte, error) {
			data, _, err := gitea.FetchMaintainershipDirFile(org, prjGit, branch, pkg)
			return data, err
		}
	}
	return m, err
}

func (data *MaintainershipMap) ListProjectMaintainers(groups []*ReviewGroup) []string {
	if data == nil {
		return nil
	}

	m, found := data.Data[ProjectKey]
	if !found {
		return nil
	}

	m = slices.Clone(m)

	// expands groups
	for _, g := range groups {
		m = g.ExpandMaintainers(m)
	}

	return m
}

func parsePkgDirData(pkg string, data []byte) []string {
	m := make(map[string][]string)
	if err := json.Unmarshal(data, &m); err != nil {
		return nil
	}

	pkgMaintainers, found := m[pkg]
	if !found {
		return nil
	}
	return pkgMaintainers
}

func (data *MaintainershipMap) ListPackageMaintainers(pkg string, groups []*ReviewGroup) []string {
	if data == nil {
		return nil
	}

	pkgMaintainers, found := data.Data[pkg]
	if !found && data.IsDir {
		pkgData, err := data.FetchPackage(pkg)
		if err == nil {
			pkgMaintainers = parsePkgDirData(pkg, pkgData)
			if len(pkgMaintainers) > 0 {
				data.Data[pkg] = pkgMaintainers
			}
		}
	}
	pkgMaintainers = slices.Clone(pkgMaintainers)
	prjMaintainers := data.ListProjectMaintainers(nil)

prjMaintainer:
	for _, prjm := range prjMaintainers {
		for i := range pkgMaintainers {
			if pkgMaintainers[i] == prjm {
				continue prjMaintainer
			}
		}
		pkgMaintainers = append(pkgMaintainers, prjm)
	}

	// expands groups
	for _, g := range groups {
		pkgMaintainers = g.ExpandMaintainers(pkgMaintainers)
	}

	return pkgMaintainers
}

func (data *MaintainershipMap) IsApproved(pkg string, reviews []*models.PullReview, submitter string, groups []*ReviewGroup) bool {
	var reviewers []string
	if pkg != ProjectKey {
		reviewers = data.ListPackageMaintainers(pkg, groups)
	} else {
		reviewers = data.ListProjectMaintainers(groups)
	}

	if len(reviewers) == 0 {
		return true
	}

	LogDebug("Looking for review by:", reviewers)
	slices.Sort(reviewers)
	reviewers = slices.Compact(reviewers)
	SubmitterIdxInReviewers := slices.Index(reviewers, submitter)
	if SubmitterIdxInReviewers > -1 && (!data.Config.ReviewRequired || len(reviewers) == 1) {
		LogDebug("Submitter is maintainer. Approving.")
		return true
	}

	for _, review := range reviews {
		if !review.Stale && review.State == ReviewStateApproved && slices.Contains(reviewers, review.User.UserName) {
			LogDebug("Reviewed by", review.User.UserName)
			return true
		}

	}
	return false
}

func (data *MaintainershipMap) modifyInplace(writer io.StringWriter) error {
	var original map[string][]string
	if err := json.Unmarshal(data.Raw, &original); err != nil {
		return err
	}

	dec := json.NewDecoder(bytes.NewReader(data.Raw))
	_, err := dec.Token()
	if err != nil {
		return err
	}

	output := ""
	lastPos := 0
	modified := false

	type entry struct {
		key      string
		valStart int
		valEnd   int
	}
	var entries []entry

	for dec.More() {
		kToken, _ := dec.Token()
		key := kToken.(string)
		var raw json.RawMessage
		dec.Decode(&raw)
		valEnd := int(dec.InputOffset())
		valStart := valEnd - len(raw)
		entries = append(entries, entry{key, valStart, valEnd})
	}

	changed := make(map[string]bool)
	for k, v := range data.Data {
		if ov, ok := original[k]; !ok || !slices.Equal(v, ov) {
			changed[k] = true
		}
	}
	for k := range original {
		if _, ok := data.Data[k]; !ok {
			changed[k] = true
		}
	}

	if len(changed) == 0 {
		_, err = writer.WriteString(string(data.Raw))
		return err
	}

	for _, e := range entries {
		if v, ok := data.Data[e.key]; ok {
			prefix := string(data.Raw[lastPos:e.valStart])
			if modified && strings.TrimSpace(output) == "{" {
				if commaIdx := strings.Index(prefix, ","); commaIdx != -1 {
					if quoteIdx := strings.Index(prefix, "\""); quoteIdx == -1 || commaIdx < quoteIdx {
						prefix = prefix[:commaIdx] + prefix[commaIdx+1:]
					}
				}
			}
			output += prefix
			if changed[e.key] {
				slices.Sort(v)
				newVal, _ := json.Marshal(v)
				output += string(newVal)
				modified = true
			} else {
				output += string(data.Raw[e.valStart:e.valEnd])
			}
		} else {
			// Deleted
			modified = true
		}
		lastPos = e.valEnd
	}
	output += string(data.Raw[lastPos:])

	// Handle additions (simplistic: at the end)
	for k, v := range data.Data {
		if _, ok := original[k]; !ok {
			slices.Sort(v)
			newVal, _ := json.Marshal(v)
			keyStr, _ := json.Marshal(k)

			// Insert before closing brace
			if idx := strings.LastIndex(output, "}"); idx != -1 {
				prefix := output[:idx]
				suffix := output[idx:]

				trimmedPrefix := strings.TrimRight(prefix, " \n\r\t")
				if !strings.HasSuffix(trimmedPrefix, "{") && !strings.HasSuffix(trimmedPrefix, ",") {
					// find the actual position of the last non-whitespace character in prefix
					lastCharIdx := strings.LastIndexAny(prefix, "]}0123456789\"")
					if lastCharIdx != -1 {
						prefix = prefix[:lastCharIdx+1] + "," + prefix[lastCharIdx+1:]
					}
				}

				insertion := fmt.Sprintf("    %s: %s", string(keyStr), string(newVal))
				if !strings.HasSuffix(prefix, "\n") {
					insertion = "\n" + insertion
				}
				output = prefix + insertion + "\n" + suffix
				modified = true
			}
		}
	}

	if modified {
		_, err := writer.WriteString(output)
		return err
	}
	_, err = writer.WriteString(string(data.Raw))
	return err
}

func (data *MaintainershipMap) WriteMaintainershipFile(writer io.StringWriter) error {
	if data.IsDir {
		return fmt.Errorf("Not implemented")
	}

	if len(data.Raw) > 0 {
		if err := data.modifyInplace(writer); err == nil {
			return nil
		}
	}

	// Fallback to full write
	writer.WriteString("{\n")
	if d, ok := data.Data[""]; ok {
		eol := ","
		if len(data.Data) == 1 {
			eol = ""
		}
		slices.Sort(d)
		str, _ := json.Marshal(d)
		writer.WriteString(fmt.Sprintf("    \"\": %s%s\n", string(str), eol))
	}

	keys := make([]string, 0, len(data.Data))
	for pkg := range data.Data {
		if pkg == "" {
			continue
		}
		keys = append(keys, pkg)
	}
	slices.Sort(keys)
	for i, pkg := range keys {
		eol := ","
		if i == len(keys)-1 {
			eol = ""
		}
		maintainers := data.Data[pkg]
		slices.Sort(maintainers)
		pkgStr, _ := json.Marshal(pkg)
		maintainersStr, _ := json.Marshal(maintainers)
		writer.WriteString(fmt.Sprintf("    %s: %s%s\n", pkgStr, maintainersStr, eol))
	}

	writer.WriteString("}\n")
	return nil
}