/**
 * Unit tests for TFLiteParser
 * Validates: Requirements 2.1, 2.2, 2.3, 2.4, 2.5, 2.6
 */

import { describe, it, expect } from 'vitest';

// ─── Lookup tables (subset for testing) ─────────────────────────────────

const BUILTIN_OPERATORS = {
    0: 'ADD', 1: 'AVERAGE_POOL_2D', 2: 'CONCATENATION', 3: 'CONV_2D',
    4: 'DEPTHWISE_CONV_2D', 9: 'FULLY_CONNECTED', 25: 'SOFTMAX', 32: 'CUSTOM'
};

const TENSOR_TYPES = {
    0: 'FLOAT32', 1: 'FLOAT16', 2: 'INT32', 3: 'UINT8',
    4: 'INT64', 5: 'STRING', 6: 'BOOL', 7: 'INT16',
    8: 'COMPLEX64', 9: 'INT8', 10: 'FLOAT64', 11: 'COMPLEX128',
    12: 'UINT64', 13: 'UINT32', 14: 'UINT16', 15: 'INT4', 16: 'BFLOAT16'
};

const BYTES_PER_ELEMENT = {
    'FLOAT32': 4, 'FLOAT16': 2, 'INT32': 4, 'UINT8': 1,
    'INT64': 8, 'STRING': 1, 'BOOL': 1, 'INT16': 2,
    'COMPLEX64': 8, 'INT8': 1, 'FLOAT64': 8, 'COMPLEX128': 16,
    'UINT64': 8, 'UINT32': 4, 'UINT16': 2, 'INT4': 0.5, 'BFLOAT16': 2
};

// ─── FlatBuffer Binary Builder ──────────────────────────────────────────
// Builds valid FlatBuffer binaries using a deferred-offset approach.
// All uoffset_t values point forward (to higher addresses).
//
// Strategy: Write tables with placeholder uoffset fields, then write
// the referenced data AFTER the table, then patch the offsets.

class FB {
    constructor() {
        this.buf = new ArrayBuffer(65536);
        this.view = new DataView(this.buf);
        this.pos = 0;
    }

    align(n) { const r = this.pos % n; if (r) this.pos += n - r; }

    u8(p, v) { this.view.setUint8(p, v); }
    u16(p, v) { this.view.setUint16(p, v, true); }
    u32(p, v) { this.view.setUint32(p, v, true); }
    i32(p, v) { this.view.setInt32(p, v, true); }

    // Patch a uoffset_t at patchPos to point to targetPos
    patch(patchPos, targetPos) {
        this.u32(patchPos, targetPos - patchPos);
    }

    writeStr(s) {
        this.align(4);
        const p = this.pos;
        const enc = new TextEncoder().encode(s);
        this.u32(p, enc.length);
        new Uint8Array(this.buf, p + 4, enc.length).set(enc);
        this.buf[p + 4 + enc.length] = 0;
        this.pos = p + 4 + enc.length + 1;
        this.align(4);
        return p;
    }

    writeI32Vec(arr) {
        this.align(4);
        const p = this.pos;
        this.u32(p, arr.length);
        for (let i = 0; i < arr.length; i++) this.i32(p + 4 + i * 4, arr[i]);
        this.pos = p + 4 + arr.length * 4;
        return p;
    }

    // Write a vector of N uoffset_t placeholders, return { vecPos, elemPositions[] }
    writeOffsetVecPlaceholder(count) {
        this.align(4);
        const p = this.pos;
        this.u32(p, count);
        this.pos += 4;
        const elems = [];
        for (let i = 0; i < count; i++) {
            elems.push(this.pos);
            this.u32(this.pos, 0); // placeholder
            this.pos += 4;
        }
        return { vecPos: p, elemPositions: elems };
    }

    /**
     * Write a vtable + table. Returns { tablePos, fieldPositions }.
     * fieldDefs: array of { type: 'u8'|'u32'|'i32'|'uoffset', value? } or null
     * For 'uoffset', value is ignored (placeholder 0 written), caller patches later.
     */
    writeTable(fieldDefs) {
        const layouts = [];
        let dataOff = 4; // after soffset_t
        for (const f of fieldDefs) {
            if (f === null) { layouts.push(null); continue; }
            const sz = f.type === 'u8' ? 1 : 4;
            const r = dataOff % sz;
            if (r) dataOff += sz - r;
            layouts.push({ off: dataOff, sz });
            dataOff += sz;
        }
        if (dataOff % 4) dataOff += 4 - (dataOff % 4);
        const objSize = dataOff;

        // Vtable
        this.align(4);
        const vtPos = this.pos;
        const vtSize = 4 + fieldDefs.length * 2;
        this.u16(vtPos, vtSize);
        this.u16(vtPos + 2, objSize);
        for (let i = 0; i < fieldDefs.length; i++) {
            this.u16(vtPos + 4 + i * 2, layouts[i] ? layouts[i].off : 0);
        }
        this.pos = vtPos + vtSize;
        this.align(4);

        // Table
        const tblPos = this.pos;
        this.i32(tblPos, tblPos - vtPos); // soffset to vtable
        this.pos = tblPos + objSize;

        // Write inline values and record field positions
        const fieldPositions = {};
        for (let i = 0; i < fieldDefs.length; i++) {
            const f = fieldDefs[i];
            const l = layouts[i];
            if (!f || !l) continue;
            const fPos = tblPos + l.off;
            fieldPositions[i] = fPos;
            switch (f.type) {
                case 'u8': this.u8(fPos, f.value || 0); break;
                case 'u32': this.u32(fPos, f.value || 0); break;
                case 'i32': this.i32(fPos, f.value || 0); break;
                case 'uoffset': this.u32(fPos, 0); break; // placeholder
            }
        }

        return { tablePos: tblPos, fieldPositions };
    }

    done() { this.align(4); return this.buf.slice(0, this.pos); }
}

/**
 * Build a valid TFLite FlatBuffer.
 * Layout order (low → high address):
 *   [root offset] [Model vtable+table] [data referenced by Model] ...
 * All uoffset_t point forward.
 */
function buildTFLiteBuffer(opts = {}) {
    const {
        version = 3, description = '',
        operatorCodes = [], tensors = [],
        operators = [], inputIndices = [], outputIndices = []
    } = opts;

    const fb = new FB();
    fb.pos = 4; // reserve root offset

    // ── Write Model table (with placeholder offsets) ──
    const model = fb.writeTable([
        { type: 'u32', value: version },                                    // 0: version
        operatorCodes.length > 0 ? { type: 'uoffset' } : null,             // 1: operator_codes
        { type: 'uoffset' },                                               // 2: subgraphs
        description ? { type: 'uoffset' } : null                           // 3: description
    ]);
    fb.u32(0, model.tablePos); // root offset

    // ── Write description string ──
    if (description && model.fieldPositions[3] !== undefined) {
        const p = fb.writeStr(description);
        fb.patch(model.fieldPositions[3], p);
    }

    // ── Write operator_codes ──
    if (operatorCodes.length > 0 && model.fieldPositions[1] !== undefined) {
        // Write operator_codes vector placeholder
        const opcVec = fb.writeOffsetVecPlaceholder(operatorCodes.length);
        fb.patch(model.fieldPositions[1], opcVec.vecPos);

        // Write each OperatorCode table AFTER the vector
        for (let i = 0; i < operatorCodes.length; i++) {
            const oc = operatorCodes[i];
            const ocTable = fb.writeTable([
                { type: 'u8', value: oc.builtinCode },                      // 0: builtin_code
                oc.customCode ? { type: 'uoffset' } : null,                 // 1: custom_code
                { type: 'i32', value: 1 }                                   // 2: version
            ]);
            fb.patch(opcVec.elemPositions[i], ocTable.tablePos);

            // Write custom_code string if present
            if (oc.customCode && ocTable.fieldPositions[1] !== undefined) {
                const p = fb.writeStr(oc.customCode);
                fb.patch(ocTable.fieldPositions[1], p);
            }
        }
    }

    // ── Write subgraphs ──
    // Subgraphs vector placeholder (1 subgraph)
    const sgVec = fb.writeOffsetVecPlaceholder(1);
    fb.patch(model.fieldPositions[2], sgVec.vecPos);

    // Write SubGraph table
    const sg = fb.writeTable([
        tensors.length > 0 ? { type: 'uoffset' } : null,                   // 0: tensors
        inputIndices.length > 0 ? { type: 'uoffset' } : null,              // 1: inputs
        outputIndices.length > 0 ? { type: 'uoffset' } : null,             // 2: outputs
        operators.length > 0 ? { type: 'uoffset' } : null,                 // 3: operators
        null                                                                 // 4: name
    ]);
    fb.patch(sgVec.elemPositions[0], sg.tablePos);

    // Write inputs vector
    if (inputIndices.length > 0 && sg.fieldPositions[1] !== undefined) {
        const p = fb.writeI32Vec(inputIndices);
        fb.patch(sg.fieldPositions[1], p);
    }

    // Write outputs vector
    if (outputIndices.length > 0 && sg.fieldPositions[2] !== undefined) {
        const p = fb.writeI32Vec(outputIndices);
        fb.patch(sg.fieldPositions[2], p);
    }

    // Write tensors
    if (tensors.length > 0 && sg.fieldPositions[0] !== undefined) {
        const tVec = fb.writeOffsetVecPlaceholder(tensors.length);
        fb.patch(sg.fieldPositions[0], tVec.vecPos);

        for (let i = 0; i < tensors.length; i++) {
            const t = tensors[i];
            const tt = fb.writeTable([
                t.shape && t.shape.length > 0 ? { type: 'uoffset' } : null, // 0: shape
                { type: 'u8', value: t.typeCode || 0 },                      // 1: type
                { type: 'u32', value: 0 },                                   // 2: buffer
                t.name ? { type: 'uoffset' } : null                          // 3: name
            ]);
            fb.patch(tVec.elemPositions[i], tt.tablePos);

            // Write shape vector
            if (t.shape && t.shape.length > 0 && tt.fieldPositions[0] !== undefined) {
                const p = fb.writeI32Vec(t.shape);
                fb.patch(tt.fieldPositions[0], p);
            }
            // Write name string
            if (t.name && tt.fieldPositions[3] !== undefined) {
                const p = fb.writeStr(t.name);
                fb.patch(tt.fieldPositions[3], p);
            }
        }
    }

    // Write operators
    if (operators.length > 0 && sg.fieldPositions[3] !== undefined) {
        const oVec = fb.writeOffsetVecPlaceholder(operators.length);
        fb.patch(sg.fieldPositions[3], oVec.vecPos);

        for (let i = 0; i < operators.length; i++) {
            const op = operators[i];
            const ot = fb.writeTable([
                { type: 'u32', value: op.opcodeIndex }                       // 0: opcode_index
            ]);
            fb.patch(oVec.elemPositions[i], ot.tablePos);
        }
    }

    return fb.done();
}

// ─── Re-implement TFLiteParser.parse() for testability ──────────────────

function _getFieldOffset(view, tablePos, fieldIndex) {
    const vtableRelOffset = view.getInt32(tablePos, true);
    const vtablePos = tablePos - vtableRelOffset;
    const vtableSize = view.getUint16(vtablePos, true);
    const fieldVtableOffset = 4 + fieldIndex * 2;
    if (fieldVtableOffset >= vtableSize) return 0;
    const fieldRelOffset = view.getUint16(vtablePos + fieldVtableOffset, true);
    if (fieldRelOffset === 0) return 0;
    return tablePos + fieldRelOffset;
}

function _ru32(view, tablePos, fi, def = 0) {
    const o = _getFieldOffset(view, tablePos, fi);
    return o === 0 ? def : view.getUint32(o, true);
}

function _ru8(view, tablePos, fi, def = 0) {
    const o = _getFieldOffset(view, tablePos, fi);
    return o === 0 ? def : view.getUint8(o);
}

function _rstr(view, tablePos, fi) {
    const o = _getFieldOffset(view, tablePos, fi);
    if (o === 0) return '';
    const rel = view.getUint32(o, true);
    const sp = o + rel;
    const len = view.getUint32(sp, true);
    return new TextDecoder('utf-8').decode(new Uint8Array(view.buffer, sp + 4, len));
}

function _rvec(view, tablePos, fi) {
    const o = _getFieldOffset(view, tablePos, fi);
    if (o === 0) return null;
    const rel = view.getUint32(o, true);
    const vp = o + rel;
    return { pos: vp + 4, length: view.getUint32(vp, true) };
}

function _ri32vec(view, tablePos, fi) {
    const v = _rvec(view, tablePos, fi);
    if (!v) return [];
    const r = [];
    for (let i = 0; i < v.length; i++) r.push(view.getInt32(v.pos + i * 4, true));
    return r;
}

function _deref(view, ep) { return ep + view.getUint32(ep, true); }

function parse(buffer) {
    try {
        if (!buffer || !(buffer instanceof ArrayBuffer) || buffer.byteLength === 0)
            return { success: false, error: 'File không hợp lệ: buffer rỗng' };
        if (buffer.byteLength < 8)
            return { success: false, error: 'File không hợp lệ: không đủ dữ liệu' };

        const view = new DataView(buffer);
        const rootOff = view.getUint32(0, true);
        if (rootOff >= buffer.byteLength || rootOff < 4)
            return { success: false, error: 'File không hợp lệ: cấu trúc FlatBuffer lỗi' };

        const mp = rootOff;
        const version = _ru32(view, mp, 0, 0);
        const description = _rstr(view, mp, 3);

        const operatorCodes = [];
        const opcVec = _rvec(view, mp, 1);
        if (opcVec) {
            for (let i = 0; i < opcVec.length; i++) {
                const ocp = _deref(view, opcVec.pos + i * 4);
                const bc = _ru8(view, ocp, 0, 0);
                const cc = _rstr(view, ocp, 1) || null;
                const name = (bc === 32 && cc) ? cc : (BUILTIN_OPERATORS[bc] || `UNKNOWN_OP_${bc}`);
                operatorCodes.push({ builtinCode: bc, customCode: cc, opcodeName: name });
            }
        }

        const sgVec = _rvec(view, mp, 2);
        const sgCount = sgVec ? sgVec.length : 0;
        let tensors = [], operators = [], inputIndices = [], outputIndices = [];

        if (sgCount > 0) {
            const sgp = _deref(view, sgVec.pos);
            const tVec = _rvec(view, sgp, 0);
            if (tVec) {
                for (let i = 0; i < tVec.length; i++) {
                    const tp = _deref(view, tVec.pos + i * 4);
                    const shape = _ri32vec(view, tp, 0);
                    const tc = _ru8(view, tp, 1, 0);
                    const name = _rstr(view, tp, 3);
                    const dtype = TENSOR_TYPES[tc] || `UNKNOWN_TYPE_${tc}`;
                    const bpe = BYTES_PER_ELEMENT[dtype] || 1;
                    const ec = shape.length > 0 ? shape.reduce((a, d) => a * Math.abs(d), 1) : 0;
                    tensors.push({ name, shape, dtype, byteSize: Math.ceil(ec * bpe) });
                }
            }
            inputIndices = _ri32vec(view, sgp, 1);
            outputIndices = _ri32vec(view, sgp, 2);
            const oVec = _rvec(view, sgp, 3);
            if (oVec) {
                for (let i = 0; i < oVec.length; i++) {
                    const op = _deref(view, oVec.pos + i * 4);
                    const oi = _ru32(view, op, 0, 0);
                    const on = oi < operatorCodes.length ? operatorCodes[oi].opcodeName : `UNKNOWN_OP_${oi}`;
                    operators.push({ opcodeName: on, opcodeIndex: oi });
                }
            }
        }

        return { success: true, data: { version, description, operators, operatorCodes,
            tensors, subgraphs: sgCount, inputIndices, outputIndices } };
    } catch (err) {
        return { success: false, error: err.message || 'Lỗi không xác định' };
    }
}

// ─── Tests ──────────────────────────────────────────────────────────────

describe('TFLiteParser - parse', () => {
    describe('Error handling (Req 2.3, 2.4, 2.5)', () => {
        it('should return error for null buffer', () => {
            expect(parse(null)).toEqual({ success: false, error: 'File không hợp lệ: buffer rỗng' });
        });
        it('should return error for undefined buffer', () => {
            expect(parse(undefined).success).toBe(false);
        });
        it('should return error for empty buffer', () => {
            expect(parse(new ArrayBuffer(0)).error).toBe('File không hợp lệ: buffer rỗng');
        });
        it('should return error for buffer < 8 bytes', () => {
            expect(parse(new ArrayBuffer(4)).error).toBe('File không hợp lệ: không đủ dữ liệu');
        });
        it('should return error for root offset out of range', () => {
            const b = new ArrayBuffer(16);
            new DataView(b).setUint32(0, 99999, true);
            expect(parse(b).success).toBe(false);
        });
        it('should return error for root offset < 4', () => {
            const b = new ArrayBuffer(16);
            new DataView(b).setUint32(0, 2, true);
            expect(parse(b).success).toBe(false);
        });
        it('should never throw for random data', () => {
            const b = new ArrayBuffer(64);
            const a = new Uint8Array(b);
            for (let i = 0; i < a.length; i++) a[i] = Math.floor(Math.random() * 256);
            const r = parse(b);
            expect(typeof r.success).toBe('boolean');
        });
    });

    describe('Successful parsing (Req 2.1, 2.2, 2.6)', () => {
        it('should parse a minimal valid TFLite buffer', () => {
            const buf = buildTFLiteBuffer({
                version: 3, description: 'Test model',
                operatorCodes: [{ builtinCode: 3 }],
                tensors: [
                    { name: 'input', shape: [1, 224, 224, 3], typeCode: 0 },
                    { name: 'output', shape: [1, 1000], typeCode: 0 }
                ],
                operators: [{ opcodeIndex: 0 }],
                inputIndices: [0], outputIndices: [1]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            expect(r.data.version).toBe(3);
            expect(r.data.description).toBe('Test model');
            expect(r.data.subgraphs).toBe(1);
        });

        it('should extract operator codes correctly', () => {
            const buf = buildTFLiteBuffer({
                operatorCodes: [{ builtinCode: 3 }, { builtinCode: 9 }, { builtinCode: 25 }],
                tensors: [{ name: 't', shape: [1], typeCode: 0 }],
                operators: [{ opcodeIndex: 0 }, { opcodeIndex: 1 }, { opcodeIndex: 2 }]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            expect(r.data.operatorCodes[0].opcodeName).toBe('CONV_2D');
            expect(r.data.operatorCodes[1].opcodeName).toBe('FULLY_CONNECTED');
            expect(r.data.operatorCodes[2].opcodeName).toBe('SOFTMAX');
        });

        it('should extract tensors with correct dtype and byteSize', () => {
            const buf = buildTFLiteBuffer({
                operatorCodes: [{ builtinCode: 0 }],
                tensors: [
                    { name: 'float_tensor', shape: [2, 3], typeCode: 0 },
                    { name: 'int8_tensor', shape: [10, 10], typeCode: 9 },
                    { name: 'uint8_tensor', shape: [5], typeCode: 3 }
                ],
                operators: [{ opcodeIndex: 0 }]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            const ft = r.data.tensors.find(t => t.name === 'float_tensor');
            expect(ft.dtype).toBe('FLOAT32');
            expect(ft.shape).toEqual([2, 3]);
            expect(ft.byteSize).toBe(24);
            const i8 = r.data.tensors.find(t => t.name === 'int8_tensor');
            expect(i8.dtype).toBe('INT8');
            expect(i8.byteSize).toBe(100);
        });

        it('should extract input and output indices', () => {
            const buf = buildTFLiteBuffer({
                operatorCodes: [{ builtinCode: 0 }],
                tensors: [{ name: 'in', shape: [1], typeCode: 0 }, { name: 'out', shape: [1], typeCode: 0 }],
                operators: [{ opcodeIndex: 0 }],
                inputIndices: [0], outputIndices: [1]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            expect(r.data.inputIndices).toEqual([0]);
            expect(r.data.outputIndices).toEqual([1]);
        });

        it('should extract operators with correct opcodeName', () => {
            const buf = buildTFLiteBuffer({
                operatorCodes: [{ builtinCode: 3 }, { builtinCode: 25 }],
                tensors: [{ name: 't', shape: [1], typeCode: 0 }],
                operators: [{ opcodeIndex: 0 }, { opcodeIndex: 0 }, { opcodeIndex: 1 }]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            expect(r.data.operators).toHaveLength(3);
            expect(r.data.operators[0].opcodeName).toBe('CONV_2D');
            expect(r.data.operators[2].opcodeName).toBe('SOFTMAX');
        });
    });

    describe('Result structure invariant (Req 2.5)', () => {
        it('should have data with all required fields when success is true', () => {
            const buf = buildTFLiteBuffer({
                operatorCodes: [{ builtinCode: 0 }],
                tensors: [{ name: 't', shape: [1], typeCode: 0 }],
                operators: [{ opcodeIndex: 0 }]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            expect(Array.isArray(r.data.operators)).toBe(true);
            expect(Array.isArray(r.data.tensors)).toBe(true);
            expect(typeof r.data.version).toBe('number');
            expect(typeof r.data.subgraphs).toBe('number');
            expect(Array.isArray(r.data.operatorCodes)).toBe(true);
            expect(Array.isArray(r.data.inputIndices)).toBe(true);
            expect(Array.isArray(r.data.outputIndices)).toBe(true);
        });
        it('should have non-empty error when success is false', () => {
            expect(parse(null).error.length).toBeGreaterThan(0);
        });
    });

    describe('Unknown types handling', () => {
        it('should display UNKNOWN_OP for unknown operator codes', () => {
            const buf = buildTFLiteBuffer({
                operatorCodes: [{ builtinCode: 250 }],
                tensors: [{ name: 't', shape: [1], typeCode: 0 }],
                operators: [{ opcodeIndex: 0 }]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            expect(r.data.operatorCodes[0].opcodeName).toBe('UNKNOWN_OP_250');
        });
        it('should display UNKNOWN_TYPE for unknown tensor types', () => {
            const buf = buildTFLiteBuffer({
                operatorCodes: [{ builtinCode: 0 }],
                tensors: [{ name: 't', shape: [1], typeCode: 99 }],
                operators: [{ opcodeIndex: 0 }]
            });
            const r = parse(buf);
            expect(r.success).toBe(true);
            expect(r.data.tensors[0].dtype).toBe('UNKNOWN_TYPE_99');
        });
    });

    describe('Lookup tables', () => {
        it('should have 17 tensor types', () => {
            expect(Object.keys(TENSOR_TYPES)).toHaveLength(17);
        });
        it('should have bytes per element for all tensor types', () => {
            for (const n of Object.values(TENSOR_TYPES)) {
                expect(BYTES_PER_ELEMENT[n]).toBeGreaterThan(0);
            }
        });
    });
});