import { Octokit } from '@octokit/rest';
import { CacheStore } from '@shared/storage/CacheStore';
import type { CachedData } from '@shared/types/CachedData';
import type {
    ContributorStats,
    ContributorUser,
    FetchResult,
    GitHubStats,
    TeamMember,
} from '@shared/types/GitHubStats';

// Constants
const CACHE_TTL = 1 * 60 * 60 * 1000; // 1 hour in milliseconds
const REPO_OWNER = 'Longhorn-Developers';
const REPO_NAME = 'UT-Registration-Plus';
const CONTRIBUTORS_API_ROUTE = `/repos/${REPO_OWNER}/${REPO_NAME}/stats/contributors`;

export const LONGHORN_DEVELOPERS_ADMINS = [
    { name: 'Sriram Hariharan', role: ['LHD Co-Founder', 'UTRP Founder'], githubUsername: 'sghsri' },
    {
        name: 'Elie Soloveichik',
        role: ['LHD Co-Founder', 'Learning and Development Director', 'UTRP Senior SWE'],
        githubUsername: 'Razboy20',
    },
    {
        name: 'Diego Perez',
        role: ['LHD Co-Founder', 'Software Engineering Director', 'UTRP Senior SWE'],
        githubUsername: 'doprz',
    },
    { name: 'Isaiah Rodriguez', role: ['LHD Co-Founder', 'President and UI/UX Director'], githubUsername: 'IsaDavRod' },
    {
        name: 'Samuel Gunter',
        role: ['Administrative Director', 'UTRP Co-Lead', 'UTRP Senior SWE'],
        githubUsername: 'Samathingamajig',
    },
    {
        name: 'Derek Chen',
        role: ['Communications Director', 'UTRP Co-Lead', 'UTRP Senior SWE'],
        githubUsername: 'DereC4',
    },
    { name: 'Kabir Ramzan', role: ['Events Director'], githubUsername: 'CMEONE' },
] as const satisfies TeamMember[];

export const LONGHORN_DEVELOPERS_SWE = [
    { name: 'Preston Cook', role: ['Software Engineer'], githubUsername: 'Preston-Cook' },
    { name: 'Ethan Lanting', role: ['Software Engineer'], githubUsername: 'EthanL06' },
    { name: 'Casey Charleston', role: ['Software Engineer'], githubUsername: 'caseycharleston' },
    { name: 'Lukas Zenick', role: ['LHD Alumni', 'Senior Software Engineer'], githubUsername: 'Lukas-Zenick' },
    { name: 'Vinson', role: ['LHD Alumni', 'Software Engineer'], githubUsername: 'vinsonzheng499' },
    { name: 'Vivek', role: ['LHD Alumni', 'Software Engineer'], githubUsername: 'vivek12311' },
] as const satisfies TeamMember[];

/**
 * Represents the GitHub usernames of the SWEs in the LONGHORN_DEVELOPERS_SWE array.
 */
export type LD_SWE_GITHUB_USERNAMES = (typeof LONGHORN_DEVELOPERS_SWE)[number]['githubUsername'];

/**
 * Represents the GitHub usernames of the admins in the LONGHORN_DEVELOPERS_ADMINS array.
 */
export type LD_ADMIN_GITHUB_USERNAMES = (typeof LONGHORN_DEVELOPERS_ADMINS)[number]['githubUsername'];

/**
 * Service for fetching GitHub statistics.
 */
export class GitHubStatsService {
    private octokit: Octokit;
    private cache: Record<string, CachedData<unknown>>;

    private storageLock: Promise<void> = Promise.resolve();

    constructor(githubToken?: string) {
        this.octokit = githubToken ? new Octokit({ auth: githubToken }) : new Octokit();
        this.cache = {} as Record<string, CachedData<unknown>>;
    }

    private async getCachedData<T>(key: string): Promise<CachedData<T> | null> {
        if (Object.keys(this.cache).length === 0) {
            const githubCache = await CacheStore.get('github');
            if (githubCache && typeof githubCache === 'object') {
                this.cache = githubCache as Record<string, CachedData<unknown>>;
            }
        }

        const cachedItem = this.cache[key] as CachedData<T> | undefined;
        if (cachedItem) {
            const timeDifference = Date.now() - cachedItem.dataFetched;
            if (timeDifference < CACHE_TTL) {
                return cachedItem;
            }
        }
        return null;
    }

    private async setCachedData<T>(key: string, data: T, persist = true): Promise<void> {
        // get the current lock
        const existingLock = this.storageLock;

        // update the lock with a new promise
        this.storageLock = (async () => {
            // wait for current lock to finish
            await existingLock;

            // ensure cache is loaded before modifying
            if (Object.keys(this.cache).length === 0) {
                const githubCache = await CacheStore.get('github');
                if (githubCache && typeof githubCache === 'object') {
                    this.cache = githubCache as Record<string, CachedData<unknown>>;
                }
            }

            // update local memory
            this.cache[key] = { data, dataFetched: Date.now() };

            // only write to the physical storage API if persist is true
            if (persist) {
                await CacheStore.set('github', this.cache);
            }
        })();

        return this.storageLock;
    }

    private async fetchWithRetry<T>(fetchFn: () => Promise<T>, retries: number = 3, delay: number = 5000): Promise<T> {
        try {
            return await fetchFn();
            // eslint-disable-next-line @typescript-eslint/no-explicit-any
        } catch (error: any) {
            if (retries > 0 && error.status === 202) {
                await new Promise(resolve => setTimeout(resolve, delay));
                return this.fetchWithRetry(fetchFn, retries - 1, delay);
            }
            throw error;
        }
    }

    private async fetchGitHub(route: string): Promise<unknown> {
        try {
            const url = new URL(route, 'https://github.cachedapi.com');
            const response = await fetch(url);
            return await response.json();
        } catch (error: unknown) {
            const url = new URL(route, 'https://api.github.com');
            const response = await fetch(url);
            return await response.json();
        }
    }

    private async fetchContributorStats(): Promise<FetchResult<ContributorStats[]>> {
        const cacheKey = `contributor_stats_${REPO_OWNER}_${REPO_NAME}`;
        const cachedStats = await this.getCachedData<ContributorStats[]>(cacheKey);

        if (cachedStats) {
            return {
                data: cachedStats.data,
                dataFetched: new Date(cachedStats.dataFetched),
                lastUpdated: new Date(),
                isCached: true,
            };
        }

        const data = await this.fetchWithRetry(() => this.fetchGitHub(CONTRIBUTORS_API_ROUTE));

        if (Array.isArray(data)) {
            const fetchResult: FetchResult<ContributorStats[]> = {
                data: data as ContributorStats[],
                dataFetched: new Date(),
                lastUpdated: new Date(),
                isCached: false,
            };
            await this.setCachedData(cacheKey, fetchResult.data);
            return fetchResult;
        }

        throw new Error('Invalid response format');
    }

    private async fetchContributorNames(contributors: string[]): Promise<Record<string, string>> {
        const names: Record<string, string> = {};

        await Promise.all(
            contributors.map(async contributor => {
                const cacheKey = `contributor_name_${contributor}`;
                const cachedName = await this.getCachedData<string>(cacheKey);
                let name = `@${contributor}`;

                if (cachedName) {
                    name = cachedName.data;
                } else {
                    try {
                        const data = (await this.fetchWithRetry(() =>
                            this.fetchGitHub(`/users/${contributor}`)
                        )) as ContributorUser;
                        if (data.name) {
                            name = data.name;
                        }
                        // Pass 'false' to avoid writing to disk for every single name
                        await this.setCachedData(cacheKey, name, false);
                    } catch (e) {
                        console.error(e);
                    }
                }
                names[contributor] = name;
            })
        );
        return names;
    }
    private async fetchMergedPRsCount(username: string): Promise<FetchResult<number>> {
        const cacheKey = `merged_prs_${username}`;
        const cachedCount = await this.getCachedData<number>(cacheKey);

        if (cachedCount !== null) {
            return {
                data: cachedCount.data,
                dataFetched: new Date(cachedCount.dataFetched),
                lastUpdated: new Date(),
                isCached: true,
            };
        }

        const { data } = await this.octokit.search.issuesAndPullRequests({
            q: `org:${REPO_OWNER} author:${username} type:pr is:merged`,
        });

        const fetchResult: FetchResult<number> = {
            data: data.total_count,
            dataFetched: new Date(),
            lastUpdated: new Date(),
            isCached: false,
        };
        await this.setCachedData(cacheKey, fetchResult.data, false);
        return fetchResult;
    }

    private processContributorStats(stats: ContributorStats): GitHubStats {
        return {
            commits: stats.total,
            linesAdded: stats.weeks.reduce((total, week) => total + week.a, 0),
            linesDeleted: stats.weeks.reduce((total, week) => total + week.d, 0),
        };
    }

    public async fetchGitHubStats(options: { includeMergedPRs?: boolean } = {}): Promise<{
        adminGitHubStats: Record<string, GitHubStats>;
        userGitHubStats: Record<string, GitHubStats>;
        contributors: string[];
        names: Record<string, string>;
        dataFetched: Date;
        lastUpdated: Date;
        isCached: boolean;
    }> {
        const { includeMergedPRs = false } = options;
        const adminGitHubStats: Record<string, GitHubStats> = {};
        const userGitHubStats: Record<string, GitHubStats> = {};
        const contributors: string[] = [];
        let oldestDataFetch = new Date();
        let newestDataFetch = new Date(0);
        let allCached = true;

        try {
            const contributorStatsResult = await this.fetchContributorStats();
            oldestDataFetch = contributorStatsResult.dataFetched;
            newestDataFetch = contributorStatsResult.dataFetched;
            allCached = contributorStatsResult.isCached;

            await Promise.all(
                contributorStatsResult.data.map(async stat => {
                    const { login } = stat.author;
                    contributors.push(login);

                    const isAdmin = LONGHORN_DEVELOPERS_ADMINS.some(admin => admin.githubUsername === login);
                    const statsObject = isAdmin ? adminGitHubStats : userGitHubStats;

                    statsObject[login] = this.processContributorStats(stat);

                    if (includeMergedPRs) {
                        try {
                            const mergedPRsResult = await this.fetchMergedPRsCount(login);
                            statsObject[login].mergedPRs = mergedPRsResult.data;

                            if (mergedPRsResult.dataFetched < oldestDataFetch) {
                                oldestDataFetch = mergedPRsResult.dataFetched;
                            }
                            if (mergedPRsResult.dataFetched > newestDataFetch) {
                                newestDataFetch = mergedPRsResult.dataFetched;
                            }
                            allCached = allCached && mergedPRsResult.isCached;
                        } catch (error) {
                            console.error(`Error fetching merged PRs for ${login}:`, error);
                            statsObject[login].mergedPRs = 0;
                        }
                    }
                })
            );

            const names = await this.fetchContributorNames(contributors);

            await CacheStore.set('github', this.cache);

            return {
                adminGitHubStats,
                userGitHubStats,
                contributors,
                names,
                dataFetched: oldestDataFetch,
                lastUpdated: new Date(),
                isCached: allCached,
            };
        } catch (error) {
            console.error('Error fetching GitHub stats:', error);
            throw error;
        }
    }
}

// /**
//  * Runs an example that fetches GitHub stats using the GitHubStatsService.
//  *
//  * @returns A promise that resolves when the example is finished running.
//  * @throws If there is an error fetching the GitHub stats.
//  */
// async function runExample() {
//     // Token is now optional
//     // const githubToken = process.env.GITHUB_TOKEN;
//     const gitHubStatsService = new GitHubStatsService();

//     try {
//         console.log('Fetching stats without merged PRs...');
//         const statsWithoutPRs = await gitHubStatsService.fetchGitHubStats();
//         console.log('Data fetched:', statsWithoutPRs.dataFetched.toLocaleString());
//         console.log('Last updated:', statsWithoutPRs.lastUpdated.toLocaleString());
//         console.log('Is cached:', statsWithoutPRs.isCached);

//         console.log(statsWithoutPRs);

//         // console.log('\nFetching stats with merged PRs...');
//         // const statsWithPRs = await gitHubStatsService.fetchGitHubStats({ includeMergedPRs: true });
//         // console.log('Data fetched:', statsWithPRs.dataFetched.toLocaleString());
//         // console.log('Last updated:', statsWithPRs.lastUpdated.toLocaleString());
//         // console.log('Is cached:', statsWithPRs.isCached);

//         // wait 5 seconds
//         // await new Promise(resolve => setTimeout(resolve, 5000));

//         // console.log('\nFetching stats again (should be cached)...');
//         // const cachedStats = await gitHubStatsService.fetchGitHubStats();
//         // console.log('Data fetched:', cachedStats.dataFetched.toLocaleString());
//         // console.log('Last updated:', cachedStats.lastUpdated.toLocaleString());
//         // console.log('Is cached:', cachedStats.isCached);
//     } catch (error) {
//         console.error('Failed to fetch GitHub stats:', error);
//     }
// }

// runExample();