package issue

import (
	"context"
	"encoding/json"
	"fmt"

	"superwork-tui/internal/gitea"
)

// knownStateFields is the authoritative set used to distinguish a state-JSON
// comment from an ordinary JSON or text comment. Must match stateJson.ts.
var knownStateFields = map[string]bool{
	"column":             true,
	"sessionId":          true,
	"implementSessionId": true,
	"reviewSessionId":    true,
	"testSessionId":      true,
	"profilePath":        true,
	"testProfilePath":    true,
	"specFile":           true,
	"planFile":           true,
	"prDiffFile":         true,
	"pr":                 true,
	"prMerged":           true,
	"prMergedAt":         true,
	"branch":             true,
	"worktreePath":       true,
	"implementStatus":    true,
	"color":              true,
	"autoReview":         true,
}

// ExtractStateJSON scans comments tail-first and returns the first comment
// body that parses as a JSON object containing at least one known state field.
// Ordinary text and JSON comments without known fields are skipped so they
// cannot shadow a real state blob. Returns an empty map when nothing matches.
//
// Exported so tests can call it without a network client.
func ExtractStateJSON(comments []gitea.Comment) map[string]any {
	for i := len(comments) - 1; i >= 0; i-- {
		body := comments[i].Body
		if body == "" {
			continue
		}
		var obj map[string]any
		if err := json.Unmarshal([]byte(body), &obj); err != nil {
			continue
		}
		for k := range obj {
			if knownStateFields[k] {
				return obj
			}
		}
	}
	return map[string]any{}
}

// stateCommenter is the subset of gitea.Client used by state-JSON operations.
type stateCommenter interface {
	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)
}

// ReadStateJSON fetches issue comments and extracts the latest state blob.
func ReadStateJSON(ctx context.Context, client stateCommenter, owner, repo string, number int) (map[string]any, error) {
	comments, err := client.ListIssueComments(ctx, owner, repo, number)
	if err != nil {
		return nil, fmt.Errorf("list comments for issue %d: %w", number, err)
	}
	return ExtractStateJSON(comments), nil
}

// MergeStateJSON reads the current state blob, merges extra on top, and posts
// a new comment containing the merged JSON.
func MergeStateJSON(ctx context.Context, client stateCommenter, owner, repo string, number int, extra map[string]any) error {
	current, err := ReadStateJSON(ctx, client, owner, repo, number)
	if err != nil {
		return err
	}
	return postMerged(ctx, client, owner, repo, number, current, extra)
}

// MergeStateJSONGuarded is like MergeStateJSON but protects done-column issues
// from having their column overwritten by a stale automated update. When the
// protection strips the only incoming field, no comment is posted.
func MergeStateJSONGuarded(
	ctx context.Context,
	client stateCommenter,
	owner, repo string,
	number int,
	extra map[string]any,
	protectDoneColumn bool,
) (posted bool, protectedDoneColumn bool, err error) {
	current, err := ReadStateJSON(ctx, client, owner, repo, number)
	if err != nil {
		return false, false, err
	}

	merged := make(map[string]any, len(extra))
	for k, v := range extra {
		merged[k] = v
	}

	if protectDoneColumn {
		if col, ok := current["column"]; ok && col == "done" {
			if incomingCol, has := merged["column"]; has && incomingCol != "done" {
				delete(merged, "column")
				protectedDoneColumn = true
			}
		}
	}

	if len(merged) == 0 {
		return false, protectedDoneColumn, nil
	}

	if err := postMerged(ctx, client, owner, repo, number, current, merged); err != nil {
		return false, protectedDoneColumn, err
	}
	return true, protectedDoneColumn, nil
}

// postMerged merges current + extra and posts the combined object as a raw
// JSON comment body (no fences — matches the TS postIssueComment call in
// stateJson.ts which passes JSON.stringify(merged) directly).
func postMerged(ctx context.Context, client stateCommenter, owner, repo string, number int, current, extra map[string]any) error {
	result := make(map[string]any, len(current)+len(extra))
	for k, v := range current {
		result[k] = v
	}
	for k, v := range extra {
		result[k] = v
	}
	b, err := json.Marshal(result)
	if err != nil {
		return fmt.Errorf("marshal state JSON: %w", err)
	}
	if _, err := client.PostIssueComment(ctx, owner, repo, number, string(b)); err != nil {
		return fmt.Errorf("post state comment on issue %d: %w", number, err)
	}
	return nil
}