package issue

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"

	"golang.org/x/sync/errgroup"
	"superwork-tui/internal/gitea"
)

// GiteaClient is the minimal interface required by this package.
// *gitea.Client satisfies it at compile time.
type GiteaClient interface {
	GetCurrentUser(ctx context.Context) (*gitea.User, error)
	ListIssuesByFilter(ctx context.Context, owner, repo, filterKey, filterVal string) ([]gitea.Issue, error)
	ListAllRepoComments(ctx context.Context, owner, repo string) ([]gitea.Comment, error)
	GetIssue(ctx context.Context, owner, repo string, number int) (*gitea.Issue, error)
	GetPullRequest(ctx context.Context, owner, repo string, number int) (*gitea.PullRequest, error)
	ListIssueComments(ctx context.Context, owner, repo string, number int) ([]gitea.Comment, error)
	PostIssueComment(ctx context.Context, owner, repo string, number int, body string) (*gitea.Comment, error)
	GetDependencies(ctx context.Context, owner, repo string, number int) ([]gitea.Issue, error)
}

// compile-time check that *gitea.Client satisfies GiteaClient.
var _ GiteaClient = (*gitea.Client)(nil)

// IsValidSpxFilePath reports whether v is a real workspace-relative markdown
// path (contains "/", ends with ".md", not a placeholder like "..." or "…").
func IsValidSpxFilePath(v string) bool {
	return v != "" &&
		strings.Contains(v, "/") &&
		strings.HasSuffix(v, ".md") &&
		v != "..." &&
		v != "…"
}

// isValidPrDiffFilePath matches the narrower rule used for prDiffFile.
func isValidPrDiffFilePath(v string) bool {
	return strings.HasPrefix(v, "docs/pr-diff/") && strings.HasSuffix(v, ".md") && !strings.Contains(v, " ")
}

func defaultColumn(state string) Column {
	if state == "open" {
		return ColumnTodo
	}
	return ColumnDone
}

// parseState extracts all issue state fields from the comment bucket.
// Returns zero values for absent or invalid fields.
func parseState(comments []gitea.Comment) (col Column, fields map[string]any) {
	state := ExtractStateJSON(comments)

	colStr, _ := state["column"].(string)
	if validColumns[Column(colStr)] {
		col = Column(colStr)
	}
	return col, state
}

func stringField(state map[string]any, key string) string {
	v, _ := state[key].(string)
	return v
}

func boolField(state map[string]any, key string) *bool {
	v, ok := state[key].(bool)
	if !ok {
		return nil
	}
	return &v
}

// numberFromIssueURL parses the trailing number from a Gitea issue_url like
// ".../issues/42".
func numberFromIssueURL(issueURL string) (int, bool) {
	parts := strings.Split(issueURL, "/")
	if len(parts) == 0 {
		return 0, false
	}
	n, err := strconv.Atoi(parts[len(parts)-1])
	if err != nil || n <= 0 {
		return 0, false
	}
	return n, true
}

// groupComments groups repo-wide comments by issue number, sorted ascending by
// creation time (Gitea returns them that way, but we sort to be safe).
func groupComments(comments []gitea.Comment) map[int][]gitea.Comment {
	buckets := make(map[int][]gitea.Comment)
	for _, c := range comments {
		n, ok := numberFromIssueURL(c.IssueURL)
		if !ok {
			continue
		}
		buckets[n] = append(buckets[n], c)
	}
	return buckets
}

// mergeIssues deduplicates two issue lists by number, preferring first seen.
func mergeIssues(a, b []gitea.Issue) []gitea.Issue {
	seen := make(map[int]bool, len(a))
	out := make([]gitea.Issue, 0, len(a)+len(b))
	for _, iss := range append(a, b...) {
		if !seen[iss.Number] {
			seen[iss.Number] = true
			out = append(out, iss)
		}
	}
	return out
}

// buildIssue assembles an Issue domain object from a Gitea issue + its comment
// bucket, resolves live PR status and prerequisite, and seeds a default state
// comment when the bucket has no state blob.
func buildIssue(
	ctx context.Context,
	client GiteaClient,
	owner, repo, workspaceRoot string,
	raw gitea.Issue,
	comments []gitea.Comment,
	prerequisite int,
	liveMerged *bool,
	liveMergedAt string,
) (*Issue, error) {
	col, state := parseState(comments)

	// When no state blob exists, fall back to issue.state and seed a comment.
	if col == "" {
		col = defaultColumn(raw.State)
		seed, _ := json.Marshal(map[string]string{"column": string(col)})
		if _, err := client.PostIssueComment(ctx, owner, repo, raw.Number, string(seed)); err != nil {
			log.Printf("[superwork] failed to seed state comment on %s/%s#%d: %v", owner, repo, raw.Number, err)
		}
	}

	specFile := stringField(state, "specFile")
	if !IsValidSpxFilePath(specFile) {
		specFile = ""
	}
	planFile := stringField(state, "planFile")
	if !IsValidSpxFilePath(planFile) {
		planFile = ""
	}
	prDiffFile := stringField(state, "prDiffFile")
	if !isValidPrDiffFilePath(prDiffFile) {
		prDiffFile = ""
	}

	// Resolve prMerged: live query wins, fall back to state JSON.
	prMerged := false
	if liveMerged != nil {
		prMerged = *liveMerged
	} else if v := boolField(state, "prMerged"); v != nil {
		prMerged = *v
	}

	mergedAt := liveMergedAt
	if mergedAt == "" {
		mergedAt = stringField(state, "prMergedAt")
	}

	worktreePath := stringField(state, "worktreePath")
	worktreeExists := false
	if worktreePath != "" && workspaceRoot != "" {
		if _, err := os.Stat(filepath.Join(workspaceRoot, worktreePath)); err == nil {
			worktreeExists = true
		}
	}

	iss := &Issue{
		Number:             raw.Number,
		Title:              raw.Title,
		Column:             col,
		SessionID:          stringField(state, "sessionId"),
		ProfilePath:        stringField(state, "profilePath"),
		TestProfilePath:    stringField(state, "testProfilePath"),
		SpecFile:           specFile,
		PlanFile:           planFile,
		PrDiffFile:         prDiffFile,
		PR:                 stringField(state, "pr"),
		PrMerged:           prMerged,
		PrMergedAt:         mergedAt,
		Branch:             stringField(state, "branch"),
		WorktreePath:       worktreePath,
		WorktreeExists:     worktreeExists,
		ImplementStatus:    stringField(state, "implementStatus"),
		ImplementSessionID: stringField(state, "implementSessionId"),
		ReviewSessionID:    stringField(state, "reviewSessionId"),
		TestSessionID:      stringField(state, "testSessionId"),
		HTMLURL:            raw.HtmlURL,
		Prerequisite:       prerequisite,
		Color:              stringField(state, "color"),
		AutoReview:         boolField(state, "autoReview"),
	}
	return iss, nil
}

// fetchPRStatus resolves live merged/mergedAt for a PR number string.
// Returns nil, "" on any failure so callers fall back to state JSON.
func fetchPRStatus(ctx context.Context, client GiteaClient, owner, repo, prStr string) (*bool, string) {
	if prStr == "" {
		return nil, ""
	}
	n, err := strconv.Atoi(prStr)
	if err != nil || n <= 0 {
		return nil, ""
	}
	pr, err := client.GetPullRequest(ctx, owner, repo, n)
	if err != nil || pr == nil {
		return nil, ""
	}
	merged := pr.Merged
	return &merged, pr.MergedAt
}

// LoadIssues loads all issues assigned to or created by the current user,
// resolves state from comment blobs, and enriches with live PR and dependency
// data (skipped for done-column issues).
func LoadIssues(ctx context.Context, client GiteaClient, owner, repo, workspaceRoot string) ([]Issue, error) {
	// Kick off user + repo-wide comments in parallel.
	userCh := make(chan *gitea.User, 1)
	userErrCh := make(chan error, 1)
	go func() {
		u, err := client.GetCurrentUser(ctx)
		if err != nil {
			userErrCh <- err
			return
		}
		userCh <- u
	}()

	commentsCh := make(chan []gitea.Comment, 1)
	commentsErrCh := make(chan error, 1)
	go func() {
		cs, err := client.ListAllRepoComments(ctx, owner, repo)
		if err != nil {
			commentsErrCh <- err
			return
		}
		commentsCh <- cs
	}()

	// Wait for user before firing filter queries.
	var user *gitea.User
	select {
	case u := <-userCh:
		user = u
	case err := <-userErrCh:
		return nil, fmt.Errorf("get current user: %w", err)
	case <-ctx.Done():
		return nil, ctx.Err()
	}

	// Assigned + created in parallel while comments may still be in flight.
	var assigned, created []gitea.Issue
	eg, egCtx := errgroup.WithContext(ctx)
	eg.Go(func() error {
		var err error
		assigned, err = client.ListIssuesByFilter(egCtx, owner, repo, "assigned_by", user.Login)
		return err
	})
	eg.Go(func() error {
		var err error
		created, err = client.ListIssuesByFilter(egCtx, owner, repo, "created_by", user.Login)
		return err
	})

	var allComments []gitea.Comment
	eg.Go(func() error {
		select {
		case cs := <-commentsCh:
			allComments = cs
			return nil
		case err := <-commentsErrCh:
			return fmt.Errorf("list repo comments: %w", err)
		case <-egCtx.Done():
			return egCtx.Err()
		}
	})
	if err := eg.Wait(); err != nil {
		return nil, err
	}

	issues := mergeIssues(assigned, created)
	buckets := groupComments(allComments)

	// Pre-compute columns to decide which issues need live PR/deps queries.
	cols := make([]Column, len(issues))
	for i, iss := range issues {
		bucket := buckets[iss.Number]
		col, _ := parseState(bucket)
		if col == "" {
			col = defaultColumn(iss.State)
		}
		cols[i] = col
	}

	// Concurrently fetch prerequisites and live PR status for non-done issues.
	prerequisites := make([]int, len(issues))
	liveMergedSlice := make([]*bool, len(issues))
	liveMergedAtSlice := make([]string, len(issues))

	eg2, eg2Ctx := errgroup.WithContext(ctx)
	for i := range issues {
		i := i
		iss := issues[i]
		if cols[i] == ColumnDone {
			continue
		}
		eg2.Go(func() error {
			deps, err := client.GetDependencies(eg2Ctx, owner, repo, iss.Number)
			if err == nil && len(deps) > 0 {
				prerequisites[i] = deps[0].Number
			}
			return nil // failures are non-fatal
		})
		eg2.Go(func() error {
			bucket := buckets[iss.Number]
			_, state := parseState(bucket)
			prStr := stringField(state, "pr")
			m, at := fetchPRStatus(eg2Ctx, client, owner, repo, prStr)
			liveMergedSlice[i] = m
			liveMergedAtSlice[i] = at
			return nil
		})
	}
	if err := eg2.Wait(); err != nil {
		return nil, err
	}

	out := make([]Issue, 0, len(issues))
	for i, raw := range issues {
		iss, err := buildIssue(
			ctx, client, owner, repo, workspaceRoot,
			raw,
			buckets[raw.Number],
			prerequisites[i],
			liveMergedSlice[i],
			liveMergedAtSlice[i],
		)
		if err != nil {
			return nil, fmt.Errorf("build issue %d: %w", raw.Number, err)
		}
		out = append(out, *iss)
	}
	return out, nil
}

// LoadSingleIssue loads one issue by number for incremental board updates.
// Returns (nil, nil) when the issue does not exist (404).
func LoadSingleIssue(ctx context.Context, client GiteaClient, owner, repo string, number int, workspaceRoot string) (*Issue, error) {
	raw, err := client.GetIssue(ctx, owner, repo, number)
	if err != nil {
		return nil, fmt.Errorf("get issue %d: %w", number, err)
	}
	if raw == nil {
		return nil, nil
	}

	var comments []gitea.Comment
	var prerequisite int
	eg, egCtx := errgroup.WithContext(ctx)
	eg.Go(func() error {
		var err error
		comments, err = client.ListIssueComments(egCtx, owner, repo, number)
		return err
	})
	eg.Go(func() error {
		deps, err := client.GetDependencies(egCtx, owner, repo, number)
		if err == nil && len(deps) > 0 {
			prerequisite = deps[0].Number
		}
		return nil // non-fatal
	})
	if err := eg.Wait(); err != nil {
		return nil, fmt.Errorf("load single issue %d: %w", number, err)
	}

	_, state := parseState(comments)
	prStr := stringField(state, "pr")
	liveMerged, liveMergedAt := fetchPRStatus(ctx, client, owner, repo, prStr)

	return buildIssue(ctx, client, owner, repo, workspaceRoot, *raw, comments, prerequisite, liveMerged, liveMergedAt)
}