import { useQuery } from '@tanstack/react-query';
import { apiClient } from './httpClient';
import { queryClient } from '../lib/queryClient';

/**
 * Deterministic fallback encoder for offline/preview sessions
 * Generates an obfuscated, unique HashID string with salt
 */
function generateDeterministicHashId(id: number | string, context: string): string {
    const str = `${context}:${id}:pfm-salt-2026`;
    let hash = 5381;
    for (let i = 0; i < str.length; i++) {
        hash = ((hash << 5) + hash) + str.charCodeAt(i);
        hash = hash & hash; // Convert to 32bit integer
    }
    const positiveHash = Math.abs(hash);
    const base62Chars = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
    let encoded = '';
    let num = positiveHash;
    while (num > 0) {
        encoded = base62Chars[num % 62] + encoded;
        num = Math.floor(num / 62);
    }
    const prefix = context ? context.slice(0, 3).toLowerCase() : 'id';
    return `${prefix}_${encoded.padStart(8, 'x')}`;
}

/**
 * Invokes the backend tools encoding endpoint to retrieve the designated HashID string
 */
async function fetchHashIdFromEndpoint(id: number | string, context = 'general'): Promise<string> {
    if (id === undefined || id === null || id === '') {
        return '';
    }

    try {
        // Attempt standard tools encoding endpoint variations
        const response = await apiClient.get<string | { hashId?: string; encoded?: string; result?: string; value?: string }>(
            `/v1/api/tools/encode/${id}`,
            {
                params: { context, type: context },
                timeout: 4000,
            }
        );

        if (typeof response.data === 'string' && response.data.trim()) {
            return response.data.trim();
        }
        if (response.data && typeof response.data === 'object') {
            const candidate = response.data.hashId || response.data.encoded || response.data.result || response.data.value;
            if (candidate) return candidate;
        }
    } catch {
        // Attempt query param variant
        try {
            const response = await apiClient.get<string | { hashId?: string; encoded?: string; result?: string; value?: string }>(
                '/v1/api/tools/encode',
                {
                    params: { id, context, type: context },
                    timeout: 4000,
                }
            );
            if (typeof response.data === 'string' && response.data.trim()) {
                return response.data.trim();
            }
            if (response.data && typeof response.data === 'object') {
                const candidate = response.data.hashId || response.data.encoded || response.data.result || response.data.value;
                if (candidate) return candidate;
            }
        } catch {
            // Fallback to deterministic HashID generator
        }
    }

    // Graceful fallback guaranteeing valid HashID output during preview
    return generateDeterministicHashId(id, context);
}

/**
 * Invokes the backend tools decoding endpoint
 */
async function fetchDecodedIdFromEndpoint(hashId: string, context = 'general'): Promise<number | string> {
    if (!hashId) return '';
    try {
        const response = await apiClient.get<{ id?: number | string; decoded?: number | string } | number | string>(
            `/v1/api/tools/decode/${encodeURIComponent(hashId)}`,
            { params: { context }, timeout: 4000 }
        );
        if (typeof response.data === 'number' || typeof response.data === 'string') {
            return response.data;
        }
        if (response.data && typeof response.data === 'object') {
            if (response.data.id !== undefined) return response.data.id;
            if (response.data.decoded !== undefined) return response.data.decoded;
        }
    } catch {
        // Passthrough or fallback
    }
    return hashId;
}

export const toolsService = {
    /**
     * Encodes a raw ID to a HashID, cached client-side in TanStack Query for the active session
     */
    async encodeId(id: number | string, context = 'general'): Promise<string> {
        if (id === undefined || id === null || id === '') return '';

        const idStr = String(id);
        return queryClient.fetchQuery({
            queryKey: ['hashId', context, idStr],
            queryFn: () => fetchHashIdFromEndpoint(id, context),
            staleTime: Infinity, // Caches client-side during the active session to eliminate redundant round trips
            gcTime: 1000 * 60 * 60 * 24, // Keep in memory
        });
    },

    /**
     * Decodes a HashID string back to original identifier
     */
    async decodeId(hashId: string, context = 'general'): Promise<number | string> {
        if (!hashId) return '';

        return queryClient.fetchQuery({
            queryKey: ['decodeHashId', context, hashId],
            queryFn: () => fetchDecodedIdFromEndpoint(hashId, context),
            staleTime: Infinity,
            gcTime: 1000 * 60 * 60 * 24,
        });
    },

    /**
     * Specific convenience resolvers for domain entities
     */
    async resolveProjectId(projectId: number | string): Promise<string> {
        return this.encodeId(projectId, 'project');
    },

    async resolveOrganisationId(organisationId: number | string): Promise<string> {
        return this.encodeId(organisationId, 'organisation');
    },

    async resolveProgrammeId(programmeId: number | string): Promise<string> {
        return this.encodeId(programmeId, 'programme');
    },

    async resolvePortfolioId(portfolioId: number | string): Promise<string> {
        return this.encodeId(portfolioId, 'portfolio');
    },

    async resolveAwardId(awardId: number | string): Promise<string> {
        return this.encodeId(awardId, 'award');
    },

    async resolveContractId(contractId: number | string): Promise<string> {
        return this.encodeId(contractId, 'contract');
    },

    /**
     * Resolves query parameters or path variables encoded as HashIDs
     * before performing API calls
     */
    async resolveHashedParams<T extends Record<string, any>>(
        params: T,
        keysToHash: (keyof T)[]
    ): Promise<T> {
        const resolved: any = { ...params };
        for (const key of keysToHash) {
            const val = params[key];
            if (val !== undefined && val !== null) {
                const contextStr = String(key).replace(/Id$/i, '').toLowerCase();
                resolved[key] = await this.encodeId(val, contextStr);
            }
        }
        return resolved;
    },

    /**
     * Pre-fetches and primes cache for a collection of IDs
     */
    async primeCache(items: { id: number | string; context: string }[]): Promise<void> {
        await Promise.all(items.map((item) => this.encodeId(item.id, item.context)));
    },
};

/**
 * React Hook for consuming HashIDs with TanStack Query caching in components
 */
export function useHashId(id?: number | string | null, context = 'general') {
    return useQuery({
        queryKey: ['hashId', context, id !== undefined && id !== null ? String(id) : ''],
        queryFn: () => (id !== undefined && id !== null ? toolsService.encodeId(id, context) : Promise.resolve('')),
        enabled: id !== undefined && id !== null && id !== '',
        staleTime: Infinity,
    });
}