/**
 * Vue Stage 2 — Generates composables from Stage 1 output.
 *
 * Subscribes to the kernel for state. Vue reactivity wraps kernel notifications.
 */

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

export function generateVueAdapter(schema) {
    const functions = schema['x-mizan-functions'] || []
    const contextGroups = schema['x-mizan-contexts'] || {}
    const mutations = functions.filter(fn => !fn.isContext && !fn.isForm && fn.affects)
    const plainFns = functions.filter(fn => !fn.isContext && !fn.isForm && !fn.affects)

    const lines = [
        '// AUTO-GENERATED by mizan — do not edit',
        '',
        "import { ref, computed, onMounted, onUnmounted, onServerPrefetch, type ComputedRef } from 'vue'",
        "import { registerContext, type ContextState } from '@mizan/runtime'",
        '',
    ]

    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('')
    }

    for (const [ctxName, ctxMeta] of Object.entries(contextGroups)) {
        const p = pascalCase(ctxName)
        const ctxFunctions = functions.filter(fn => fn.isContext === ctxName)
        const paramEntries = Object.entries(ctxMeta.params || {})
        const paramsArg = paramEntries.length > 0 ? 'params' : '{} as any'

        if (paramEntries.length > 0) {
            lines.push(`export function use${p}Context(params: ${p}ContextParams) {`)
        } else {
            lines.push(`export function use${p}Context() {`)
        }

        lines.push(`    const state = ref<ContextState<${p}ContextData>>({ data: null, status: 'idle', error: null })`)
        lines.push(`    let handle: ReturnType<typeof registerContext> | null = null`)
        lines.push('')
        lines.push(`    onMounted(() => {`)
        lines.push(`        handle = registerContext('${ctxName}', ${paramsArg}, () => fetch${p}Context(${paramsArg}))`)
        lines.push(`        handle.subscribe(() => { state.value = handle!.getState() })`)
        lines.push(`        handle.refetch()`)
        lines.push(`    })`)
        lines.push('')
        lines.push(`    onServerPrefetch(async () => {`)
        lines.push(`        handle = registerContext('${ctxName}', ${paramsArg}, () => fetch${p}Context(${paramsArg}))`)
        lines.push(`        await handle.refetch()`)
        lines.push(`        state.value = handle.getState()`)
        lines.push(`    })`)
        lines.push('')
        lines.push(`    onUnmounted(() => { handle?.unregister() })`)
        lines.push('')
        lines.push(`    return {`)
        lines.push(`        state,`)
        for (const fn of ctxFunctions) {
            lines.push(`        ${fn.camelName}: computed(() => state.value.data?.${fn.name} ?? null) as ComputedRef<${fn.outputType} | null>,`)
        }
        lines.push(`        loading: computed(() => state.value.status === 'loading'),`)
        lines.push(`        error: computed(() => state.value.error),`)
        lines.push(`    }`)
        lines.push('}')
        lines.push('')
    }

    for (const fn of [...mutations, ...plainFns]) {
        const p = pascalCase(fn.camelName)
        lines.push(`export function use${p}() {`)
        lines.push(`    const isPending = ref(false)`)
        lines.push(`    const error = ref<Error | null>(null)`)
        if (fn.hasInput) {
            lines.push(`    async function mutate(args: Parameters<typeof call${p}>[0]) {`)
        } else {
            lines.push(`    async function mutate() {`)
        }
        lines.push(`        isPending.value = true; error.value = null`)
        lines.push(`        try { return await call${p}(${fn.hasInput ? 'args' : ''}) }`)
        lines.push(`        catch (e) { error.value = e as Error; throw e }`)
        lines.push(`        finally { isPending.value = false }`)
        lines.push(`    }`)
        lines.push(`    return { mutate, isPending, error }`)
        lines.push('}')
        lines.push('')
    }

    lines.push("export type { ContextState } from '@mizan/runtime'")
    lines.push("export { configure, initSession, MizanError } from '@mizan/runtime'")
    lines.push('')

    return lines.join('\n')
}