/**
 * React Stage 2 — Generates hooks + context providers from Stage 1 output.
 */

function pascalCase(str) {
    return str.split(/[.\-_]/).map(p => p.charAt(0).toUpperCase() + p.slice(1)).join('')
}

export function generateReactAdapter(schema) {
    const functions = schema['x-mizan-functions'] || []
    const contextGroups = schema['x-mizan-contexts'] || {}
    const namedContexts = Object.entries(contextGroups).filter(([n]) => n !== 'global')
    const globalContexts = functions.filter(fn => fn.isContext === 'global')
    const mutations = functions.filter(fn => !fn.isContext && !fn.isForm && fn.affects)
    const plainFns = functions.filter(fn => !fn.isContext && !fn.isForm && !fn.affects)

    const lines = [
        "'use client'",
        '',
        '// AUTO-GENERATED by mizan — do not edit',
        '',
        "import { createContext, useContext, useState, useEffect, useCallback, type ReactNode } from 'react'",
        "import { registerContext, mizanCall, mizanFetch } from '@mizan/runtime'",
        '',
    ]

    // Import from Stage 1
    const stage1Imports = []
    for (const [ctxName] of Object.entries(contextGroups)) {
        const p = pascalCase(ctxName)
        stage1Imports.push(`fetch${p}Context`, `type ${p}ContextData`, `type ${p}ContextParams`)
    }
    for (const fn of [...mutations, ...plainFns]) {
        stage1Imports.push(`call${pascalCase(fn.camelName)}`)
    }
    if (stage1Imports.length > 0) {
        lines.push(`import { ${stage1Imports.join(', ')} } from '../index'`)
        lines.push('')
    }

    // ── Global context hooks ────────────────────────────────────────────

    if (globalContexts.length > 0) {
        const p = pascalCase('global')

        lines.push(`// Global context — fetched once at app init`)
        lines.push(`const GlobalCtx = createContext<${p}ContextData | null>(null)`)
        lines.push('')

        lines.push(`export function GlobalContextProvider({ children }: { children: ReactNode }) {`)
        lines.push(`    const [data, setData] = useState<${p}ContextData | null>(() => {`)
        lines.push(`        if (typeof window === 'undefined') return null`)
        lines.push(`        const ssr = (window as any).__MIZAN_SSR_DATA__`)
        lines.push(`        return ssr ?? null`)
        lines.push(`    })`)
        lines.push('')
        lines.push(`    const refetch = useCallback(async () => {`)
        lines.push(`        const result = await fetch${p}Context({} as any)`)
        lines.push(`        setData(result)`)
        lines.push(`    }, [])`)
        lines.push('')
        lines.push(`    useEffect(() => { if (!data) refetch() }, [data, refetch])`)
        lines.push(`    useEffect(() => registerContext('global', {}, refetch), [refetch])`)
        lines.push('')
        lines.push(`    return <GlobalCtx.Provider value={data}>{children}</GlobalCtx.Provider>`)
        lines.push('}')
        lines.push('')

        for (const fn of globalContexts) {
            const hookPascal = pascalCase(fn.camelName)
            lines.push(`export function use${hookPascal}(): ${fn.outputType} {`)
            lines.push(`    const ctx = useContext(GlobalCtx)`)
            lines.push(`    if (!ctx) throw new Error('use${hookPascal} requires GlobalContextProvider')`)
            lines.push(`    return ctx.${fn.name}`)
            lines.push('}')
            lines.push('')
        }
    }

    // ── Named context providers ─────────────────────────────────────────

    for (const [ctxName, ctxMeta] of namedContexts) {
        const p = pascalCase(ctxName)
        const ctxFunctions = functions.filter(fn => fn.isContext === ctxName)
        const paramEntries = Object.entries(ctxMeta.params || {})

        lines.push(`// ${p} context`)
        lines.push(`const ${p}Ctx = createContext<${p}ContextData | null>(null)`)
        lines.push('')

        // Provider
        lines.push(`export function ${p}Context({ children, ...params }: ${p}ContextParams & { children: ReactNode }) {`)
        lines.push(`    const [data, setData] = useState<${p}ContextData | null>(() => {`)
        lines.push(`        if (typeof window === 'undefined') return null`)
        lines.push(`        const ssr = (window as any).__MIZAN_SSR_DATA__`)
        if (ctxFunctions.length > 0) {
            lines.push(`        if (ssr?.${ctxFunctions[0].name} !== undefined) return ssr`)
        }
        lines.push(`        return null`)
        lines.push(`    })`)
        lines.push('')
        lines.push(`    const refetch = useCallback(async () => {`)
        lines.push(`        const result = await fetch${p}Context(params)`)
        lines.push(`        setData(result)`)

        const deps = paramEntries.map(([pName]) => `params.${pName}`)
        lines.push(`    }, [${deps.join(', ')}])`)
        lines.push('')
        lines.push(`    useEffect(() => { if (!data) refetch() }, [data, refetch])`)
        lines.push(`    useEffect(() => registerContext('${ctxName}', params, refetch), [${deps.join(', ')}, refetch])`)
        lines.push('')
        lines.push(`    return <${p}Ctx.Provider value={data}>{children}</${p}Ctx.Provider>`)
        lines.push('}')
        lines.push('')

        // Hooks
        for (const fn of ctxFunctions) {
            const hookPascal = pascalCase(fn.camelName)
            lines.push(`export function use${hookPascal}(): ${fn.outputType} | null {`)
            lines.push(`    const ctx = useContext(${p}Ctx)`)
            lines.push(`    return ctx?.${fn.name} ?? null`)
            lines.push('}')
            lines.push('')
        }
    }

    // ── Mutation hooks ──────────────────────────────────────────────────

    for (const fn of mutations) {
        const p = pascalCase(fn.camelName)
        if (fn.hasInput) {
            lines.push(`export function use${p}() {`)
            lines.push(`    return useCallback((args: Parameters<typeof call${p}>[0]) => call${p}(args), [])`)
            lines.push('}')
        } else {
            lines.push(`export function use${p}() {`)
            lines.push(`    return useCallback(() => call${p}(), [])`)
            lines.push('}')
        }
        lines.push('')
    }

    // ── Plain function hooks ────────────────────────────────────────────

    for (const fn of plainFns) {
        const p = pascalCase(fn.camelName)
        if (fn.hasInput) {
            lines.push(`export function use${p}() {`)
            lines.push(`    return useCallback((args: Parameters<typeof call${p}>[0]) => call${p}(args), [])`)
            lines.push('}')
        } else {
            lines.push(`export function use${p}() {`)
            lines.push(`    return useCallback(() => call${p}(), [])`)
            lines.push('}')
        }
        lines.push('')
    }

    return lines.join('\n')
}